Vulnerability-Lookup

CVE-2026-55531 (GCVE-0-2026-55531)

Vulnerability from cvelistv5 – Published: 2026-08-25 14:33 – Updated: 2026-08-25 16:14

Title

PraisonAI: Unauthenticated unbounded session accumulation in the PraisonAI MCP HTTP server (memory exhaustion; session TTL never enforced)

Summary

PraisonAI is a multi-agent teams system. Prior to praisonai 4.6.58, the MCP HTTP Stream mcp_post handler creates a new _sessions entry for every initialize request but does not call _cleanup_sessions or enforce a maximum. An unauthenticated caller can exhaust memory. The fix invokes cleanup and limits sessions through PRAISONAI_MCP_MAX_SESSIONS. This issue is fixed in version 4.6.58.

Severity

6.5 (Medium)


                        
                          CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H

SSVC

Exploitation: poc Automatable: no Technical Impact: partial

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-08-25 16:13 UTC

CWE

CWE-400 - Uncontrolled Resource Consumption
CWE-770 - Allocation of Resources Without Limits or Throttling

Assigner

GitHub_M CNA under the mitre root

CNA scorecard C 72/100 over 7613 records in the last 180 days details

References

3 references

URL	Tags
https://github.com/MervinPraison/PraisonAI/securi…	x_refsource_CONFIRM
https://github.com/MervinPraison/PraisonAI/commit…	x_refsource_MISC
https://github.com/MervinPraison/PraisonAI/releas…	x_refsource_MISC

Impacted products

1 product

Vendor	Product	Version	CPE status
MervinPraison	PraisonAI	Affected: < 4.6.58	guessed

Show details on NVD website

JSON

To clipboard

{
  "containers": {
    "adp": [
      {
        "metrics": [
          {
            "other": {
              "content": {
                "id": "CVE-2026-55531",
                "options": [
                  {
                    "Exploitation": "poc"
                  },
                  {
                    "Automatable": "no"
                  },
                  {
                    "Technical Impact": "partial"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-08-25T16:13:49.692230Z",
                "version": "2.0.3"
              },
              "type": "ssvc"
            }
          }
        ],
        "providerMetadata": {
          "dateUpdated": "2026-08-25T16:14:09.460Z",
          "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "shortName": "CISA-ADP"
        },
        "references": [
          {
            "tags": [
              "exploit"
            ],
            "url": "https://github.com/MervinPraison/PraisonAI/security/advisories/GHSA-wv94-5qcp-6m36"
          }
        ],
        "title": "CISA ADP Vulnrichment"
      }
    ],
    "cna": {
      "affected": [
        {
          "product": "PraisonAI",
          "vendor": "MervinPraison",
          "versions": [
            {
              "status": "affected",
              "version": "\u003c 4.6.58"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "PraisonAI is a multi-agent teams system. Prior to praisonai 4.6.58, the MCP HTTP Stream mcp_post handler creates a new _sessions entry for every initialize request but does not call _cleanup_sessions or enforce a maximum. An unauthenticated caller can exhaust memory. The fix invokes cleanup and limits sessions through PRAISONAI_MCP_MAX_SESSIONS. This issue is fixed in version 4.6.58."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "attackComplexity": "LOW",
            "attackVector": "NETWORK",
            "availabilityImpact": "HIGH",
            "baseScore": 6.5,
            "baseSeverity": "MEDIUM",
            "confidentialityImpact": "NONE",
            "integrityImpact": "NONE",
            "privilegesRequired": "NONE",
            "scope": "UNCHANGED",
            "userInteraction": "REQUIRED",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H",
            "version": "3.1"
          }
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "cweId": "CWE-400",
              "description": "CWE-400: Uncontrolled Resource Consumption",
              "lang": "en",
              "type": "CWE"
            }
          ]
        },
        {
          "descriptions": [
            {
              "cweId": "CWE-770",
              "description": "CWE-770: Allocation of Resources Without Limits or Throttling",
              "lang": "en",
              "type": "CWE"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-25T14:33:51.733Z",
        "orgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
        "shortName": "GitHub_M"
      },
      "references": [
        {
          "name": "https://github.com/MervinPraison/PraisonAI/security/advisories/GHSA-wv94-5qcp-6m36",
          "tags": [
            "x_refsource_CONFIRM"
          ],
          "url": "https://github.com/MervinPraison/PraisonAI/security/advisories/GHSA-wv94-5qcp-6m36"
        },
        {
          "name": "https://github.com/MervinPraison/PraisonAI/commit/2f9677abb2ea68eab864ee8b6a828fd0141612e1",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/MervinPraison/PraisonAI/commit/2f9677abb2ea68eab864ee8b6a828fd0141612e1"
        },
        {
          "name": "https://github.com/MervinPraison/PraisonAI/releases/tag/v4.6.58",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/MervinPraison/PraisonAI/releases/tag/v4.6.58"
        }
      ],
      "source": {
        "advisory": "GHSA-wv94-5qcp-6m36",
        "discovery": "UNKNOWN"
      },
      "title": "PraisonAI: Unauthenticated unbounded session accumulation in the PraisonAI MCP HTTP server (memory exhaustion; session TTL never enforced)"
    }
  },
  "cveMetadata": {
    "assignerOrgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
    "assignerShortName": "GitHub_M",
    "cveId": "CVE-2026-55531",
    "datePublished": "2026-08-25T14:33:51.733Z",
    "dateReserved": "2026-06-16T23:01:04.073Z",
    "dateUpdated": "2026-08-25T16:14:09.460Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
    "epss": {
      "cve": "CVE-2026-55531",
      "date": "2026-10-19",
      "epss": "0.00452",
      "percentile": "0.37916"
    },
    "nvd": {
      "cve": {
        "affected": [
          {
            "affectedData": [
              {
                "product": "PraisonAI",
                "vendor": "MervinPraison",
                "versions": [
                  {
                    "status": "affected",
                    "version": "\u003c 4.6.58"
                  }
                ]
              }
            ],
            "source": "security-advisories@github.com"
          }
        ],
        "cveTags": [],
        "descriptions": [
          {
            "lang": "en",
            "value": "PraisonAI is a multi-agent teams system. Prior to praisonai 4.6.58, the MCP HTTP Stream mcp_post handler creates a new _sessions entry for every initialize request but does not call _cleanup_sessions or enforce a maximum. An unauthenticated caller can exhaust memory. The fix invokes cleanup and limits sessions through PRAISONAI_MCP_MAX_SESSIONS. This issue is fixed in version 4.6.58."
          }
        ],
        "id": "CVE-2026-55531",
        "lastModified": "2026-09-09T21:07:31.353",
        "metrics": {
          "cvssMetricV31": [
            {
              "cvssData": {
                "attackComplexity": "LOW",
                "attackVector": "NETWORK",
                "availabilityImpact": "HIGH",
                "baseScore": 6.5,
                "baseSeverity": "MEDIUM",
                "confidentialityImpact": "NONE",
                "integrityImpact": "NONE",
                "privilegesRequired": "NONE",
                "scope": "UNCHANGED",
                "userInteraction": "REQUIRED",
                "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H",
                "version": "3.1"
              },
              "exploitabilityScore": 2.8,
              "impactScore": 3.6,
              "source": "security-advisories@github.com",
              "type": "Secondary"
            }
          ],
          "ssvcV203": [
            {
              "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
              "ssvcData": {
                "id": "CVE-2026-55531",
                "options": [
                  {
                    "exploitation": "poc"
                  },
                  {
                    "automatable": "no"
                  },
                  {
                    "technicalImpact": "partial"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-08-25T16:13:49.692230Z",
                "version": "2.0.3"
              }
            }
          ]
        },
        "published": "2026-08-25T15:16:34.017",
        "references": [
          {
            "source": "security-advisories@github.com",
            "url": "https://github.com/MervinPraison/PraisonAI/commit/2f9677abb2ea68eab864ee8b6a828fd0141612e1"
          },
          {
            "source": "security-advisories@github.com",
            "url": "https://github.com/MervinPraison/PraisonAI/releases/tag/v4.6.58"
          },
          {
            "source": "security-advisories@github.com",
            "url": "https://github.com/MervinPraison/PraisonAI/security/advisories/GHSA-wv94-5qcp-6m36"
          },
          {
            "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
            "url": "https://github.com/MervinPraison/PraisonAI/security/advisories/GHSA-wv94-5qcp-6m36"
          }
        ],
        "sourceIdentifier": "security-advisories@github.com",
        "vulnStatus": "Deferred",
        "weaknesses": [
          {
            "description": [
              {
                "lang": "en",
                "value": "CWE-400"
              },
              {
                "lang": "en",
                "value": "CWE-770"
              }
            ],
            "source": "security-advisories@github.com",
            "type": "Secondary"
          }
        ]
      }
    },
    "vulnrichment": {
      "containers": {
        "adp": [
          {
            "metrics": [
              {
                "other": {
                  "content": {
                    "id": "CVE-2026-55531",
                    "options": [
                      {
                        "Exploitation": "poc"
                      },
                      {
                        "Automatable": "no"
                      },
                      {
                        "Technical Impact": "partial"
                      }
                    ],
                    "role": "CISA Coordinator",
                    "timestamp": "2026-08-25T16:13:49.692230Z",
                    "version": "2.0.3"
                  },
                  "type": "ssvc"
                }
              }
            ],
            "providerMetadata": {
              "dateUpdated": "2026-08-25T16:14:06.455Z",
              "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
              "shortName": "CISA-ADP"
            },
            "references": [
              {
                "tags": [
                  "exploit"
                ],
                "url": "https://github.com/MervinPraison/PraisonAI/security/advisories/GHSA-wv94-5qcp-6m36"
              }
            ],
            "title": "CISA ADP Vulnrichment"
          }
        ],
        "cna": {
          "affected": [
            {
              "product": "PraisonAI",
              "vendor": "MervinPraison",
              "versions": [
                {
                  "status": "affected",
                  "version": "\u003c 4.6.58"
                }
              ]
            }
          ],
          "descriptions": [
            {
              "lang": "en",
              "value": "PraisonAI is a multi-agent teams system. Prior to praisonai 4.6.58, the MCP HTTP Stream mcp_post handler creates a new _sessions entry for every initialize request but does not call _cleanup_sessions or enforce a maximum. An unauthenticated caller can exhaust memory. The fix invokes cleanup and limits sessions through PRAISONAI_MCP_MAX_SESSIONS. This issue is fixed in version 4.6.58."
            }
          ],
          "metrics": [
            {
              "cvssV3_1": {
                "attackComplexity": "LOW",
                "attackVector": "NETWORK",
                "availabilityImpact": "HIGH",
                "baseScore": 6.5,
                "baseSeverity": "MEDIUM",
                "confidentialityImpact": "NONE",
                "integrityImpact": "NONE",
                "privilegesRequired": "NONE",
                "scope": "UNCHANGED",
                "userInteraction": "REQUIRED",
                "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H",
                "version": "3.1"
              }
            }
          ],
          "problemTypes": [
            {
              "descriptions": [
                {
                  "cweId": "CWE-400",
                  "description": "CWE-400: Uncontrolled Resource Consumption",
                  "lang": "en",
                  "type": "CWE"
                }
              ]
            },
            {
              "descriptions": [
                {
                  "cweId": "CWE-770",
                  "description": "CWE-770: Allocation of Resources Without Limits or Throttling",
                  "lang": "en",
                  "type": "CWE"
                }
              ]
            }
          ],
          "providerMetadata": {
            "dateUpdated": "2026-08-25T14:33:51.733Z",
            "orgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
            "shortName": "GitHub_M"
          },
          "references": [
            {
              "name": "https://github.com/MervinPraison/PraisonAI/security/advisories/GHSA-wv94-5qcp-6m36",
              "tags": [
                "x_refsource_CONFIRM"
              ],
              "url": "https://github.com/MervinPraison/PraisonAI/security/advisories/GHSA-wv94-5qcp-6m36"
            },
            {
              "name": "https://github.com/MervinPraison/PraisonAI/commit/2f9677abb2ea68eab864ee8b6a828fd0141612e1",
              "tags": [
                "x_refsource_MISC"
              ],
              "url": "https://github.com/MervinPraison/PraisonAI/commit/2f9677abb2ea68eab864ee8b6a828fd0141612e1"
            },
            {
              "name": "https://github.com/MervinPraison/PraisonAI/releases/tag/v4.6.58",
              "tags": [
                "x_refsource_MISC"
              ],
              "url": "https://github.com/MervinPraison/PraisonAI/releases/tag/v4.6.58"
            }
          ],
          "source": {
            "advisory": "GHSA-wv94-5qcp-6m36",
            "discovery": "UNKNOWN"
          },
          "title": "PraisonAI: Unauthenticated unbounded session accumulation in the PraisonAI MCP HTTP server (memory exhaustion; session TTL never enforced)"
        }
      },
      "cveMetadata": {
        "assignerOrgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
        "assignerShortName": "GitHub_M",
        "cveId": "CVE-2026-55531",
        "datePublished": "2026-08-25T14:33:51.733Z",
        "dateReserved": "2026-06-16T23:01:04.073Z",
        "dateUpdated": "2026-08-25T16:14:09.460Z",
        "state": "PUBLISHED"
      },
      "dataType": "CVE_RECORD",
      "dataVersion": "5.2"
    }
  }
}

FKIE_CVE-2026-55531

Vulnerability from fkie_nvd - Published: 2026-08-25 15:16 - Updated: 2026-09-09 21:07

Severity

6.5 (Medium) - CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H

Summary

References

	URL	Tags
	security-advisories@github.com	https://github.com/MervinPraison/PraisonAI/commit/2f9677abb2ea68eab864ee8b6a828fd0141612e1
	security-advisories@github.com	https://github.com/MervinPraison/PraisonAI/releases/tag/v4.6.58
	security-advisories@github.com	https://github.com/MervinPraison/PraisonAI/security/advisories/GHSA-wv94-5qcp-6m36
	134c704f-9b21-4f2e-91b3-4a467353bcc0	https://github.com/MervinPraison/PraisonAI/security/advisories/GHSA-wv94-5qcp-6m36

Impacted products

	Vendor	Product	Version

JSON

To clipboard

{
  "affected": [
    {
      "affectedData": [
        {
          "product": "PraisonAI",
          "vendor": "MervinPraison",
          "versions": [
            {
              "status": "affected",
              "version": "\u003c 4.6.58"
            }
          ]
        }
      ],
      "source": "security-advisories@github.com"
    }
  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "PraisonAI is a multi-agent teams system. Prior to praisonai 4.6.58, the MCP HTTP Stream mcp_post handler creates a new _sessions entry for every initialize request but does not call _cleanup_sessions or enforce a maximum. An unauthenticated caller can exhaust memory. The fix invokes cleanup and limits sessions through PRAISONAI_MCP_MAX_SESSIONS. This issue is fixed in version 4.6.58."
    }
  ],
  "id": "CVE-2026-55531",
  "lastModified": "2026-09-09T21:07:31.353",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
          "attackComplexity": "LOW",
          "attackVector": "NETWORK",
          "availabilityImpact": "HIGH",
          "baseScore": 6.5,
          "baseSeverity": "MEDIUM",
          "confidentialityImpact": "NONE",
          "integrityImpact": "NONE",
          "privilegesRequired": "NONE",
          "scope": "UNCHANGED",
          "userInteraction": "REQUIRED",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H",
          "version": "3.1"
        },
        "exploitabilityScore": 2.8,
        "impactScore": 3.6,
        "source": "security-advisories@github.com",
        "type": "Secondary"
      }
    ],
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "id": "CVE-2026-55531",
          "options": [
            {
              "exploitation": "poc"
            },
            {
              "automatable": "no"
            },
            {
              "technicalImpact": "partial"
            }
          ],
          "role": "CISA Coordinator",
          "timestamp": "2026-08-25T16:13:49.692230Z",
          "version": "2.0.3"
        }
      }
    ]
  },
  "published": "2026-08-25T15:16:34.017",
  "references": [
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/MervinPraison/PraisonAI/commit/2f9677abb2ea68eab864ee8b6a828fd0141612e1"
    },
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/MervinPraison/PraisonAI/releases/tag/v4.6.58"
    },
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/MervinPraison/PraisonAI/security/advisories/GHSA-wv94-5qcp-6m36"
    },
    {
      "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
      "url": "https://github.com/MervinPraison/PraisonAI/security/advisories/GHSA-wv94-5qcp-6m36"
    }
  ],
  "sourceIdentifier": "security-advisories@github.com",
  "vulnStatus": "Deferred",
  "weaknesses": [
    {
      "description": [
        {
          "lang": "en",
          "value": "CWE-400"
        },
        {
          "lang": "en",
          "value": "CWE-770"
        }
      ],
      "source": "security-advisories@github.com",
      "type": "Secondary"
    }
  ]
}

GHSA-WV94-5QCP-6M36

Vulnerability from github – Published: 2026-08-25 14:34 – Updated: 2026-08-25 14:34

Summary

PraisonAI MCP HTTP server has unauthenticated unbounded session accumulation (memory exhaustion; session TTL never enforced)

Details

Summary

The PraisonAI MCP HTTP-stream server creates a new in-memory session on every initialize request and never removes it. The cleanup routine that would expire sessions (_cleanup_sessions) is defined but never called anywhere in the codebase, and the configured session TTL is never enforced. There is no cap on the number of sessions. Because initialize requires no authentication and the server keeps every session dictionary forever, an attacker who can reach the endpoint (directly when the server is bound to a routable address, or from a victim's browser via the separate Origin-validation bypass) can drive memory usage up without bound until the process is killed by the out-of-memory killer. The same unbounded-growth pattern also applies to the cancelled-requests set populated by notifications/cancelled.

Details

In transports/http_stream.py, each initialize creates and stores a session with no limit:

if body.get("method") == "initialize":
    new_session_id = str(uuid.uuid4())
    self._sessions[new_session_id] = {
        "created_at": time.time(),
        "last_activity": time.time(),
    }

A cleanup method exists:

def _cleanup_sessions(self) -> None:
    now = time.time()
    expired = [sid for sid, data in self._sessions.items()
               if now - data["last_activity"] > self.session_ttl]
    for sid in expired:
        del self._sessions[sid]

but grep across the package shows it has no call sites: it is never invoked on a timer, on request handling, or from any background task. self.session_ttl (default 3600) is stored and otherwise unused. There is no maximum-session check anywhere on the write path. As a result self._sessions grows monotonically for the lifetime of the process.

initialize is unauthenticated: in mcp_post the API-key check is skipped when no key is configured (the default), and initialize does not require a prior session. The Origin check is the only gate, and a request with no Origin header is allowed; additionally the Origin allowlist is bypassable (see the companion report on the startswith Origin-validation bypass), so the endpoint is reachable from a malicious web page as well as directly.

The server-side cancellation set in server.py has the same defect:

if method == "notifications/cancelled":
    request_id = params.get("requestId")
    if request_id:
        self._cancelled_requests.add(str(request_id))   # never cleared

self._cancelled_requests is an unbounded set that is added to but never pruned.

PoC

scripts/poc_mcp_session_dos.sh. Start the server (default config, no API key):

praisonai mcp serve --transport http-stream --host 127.0.0.1 --port 8080

Send repeated initialize requests and watch the active session count grow:

for i in $(seq 1 200); do
  curl -s -o /dev/null -X POST http://127.0.0.1:8080/mcp \
    -H 'Content-Type: application/json' -H 'Origin: http://localhost' \
    -d '{"jsonrpc":"2.0","id":1,"method":"initialize","params":{"protocolVersion":"2025-06-18","capabilities":{},"clientInfo":{"name":"x","version":"1"}}}'
done
curl -s http://127.0.0.1:8080/health

Observed on 4.6.52 after 200 requests:

{"status":"healthy","server":"praisonai","version":"1.0.0","protocol_version":"2025-11-25","active_sessions":200}

The count rises by one per request and never decreases; there is no TTL expiry and no cap. Sustained requests grow the process resident set without bound. Each session also retains any SSE event history keyed by session id, amplifying the per-session footprint.

Impact

An unauthenticated client can exhaust the memory of the host running the MCP server, leading to denial of service (the process is terminated by the OOM killer, taking down the agent endpoint). When the server is bound to a routable interface (for example --host 0.0.0.0, common in containers), this is a direct remote unauthenticated DoS. With the default localhost bind, it is reachable from any web page the operator visits, because initialize is unauthenticated and the Origin gate is bypassable. The defect is a missing cleanup wiring plus the absence of any session cap, so it manifests even under benign long-running use.

Remediation

Enforce the session TTL and cap the number of concurrent sessions: call _cleanup_sessions periodically (a background asyncio task, or opportunistically on each request) and reject new sessions with a 429/503 once a configurable maximum is reached. Bound _cancelled_requests similarly (for example an LRU or a periodic prune keyed by age), since it is also never cleared. Require authentication by default on the HTTP-stream transport so that anonymous clients cannot create sessions at all.

Severity

6.5 (Medium)


                  
                    CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H

Show details on source website

JSON

To clipboard

{
  "affected": [
    {
      "package": {
        "ecosystem": "PyPI",
        "name": "PraisonAI"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "4.6.58"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-55531"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-400",
      "CWE-770"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-08-25T14:34:28Z",
    "nvd_published_at": null,
    "severity": "MODERATE"
  },
  "details": "### Summary\n\nThe PraisonAI MCP HTTP-stream server creates a new in-memory session on every initialize request and never removes it. The cleanup routine that would expire sessions (_cleanup_sessions) is defined but never called anywhere in the codebase, and the configured session TTL is never enforced. There is no cap on the number of sessions. Because initialize requires no authentication and the server keeps every session dictionary forever, an attacker who can reach the endpoint (directly when the server is bound to a routable address, or from a victim\u0027s browser via the separate Origin-validation bypass) can drive memory usage up without bound until the process is killed by the out-of-memory killer. The same unbounded-growth pattern also applies to the cancelled-requests set populated by notifications/cancelled.\n\n### Details\n\nIn transports/http_stream.py, each initialize creates and stores a session with no limit:\n\n```python\nif body.get(\"method\") == \"initialize\":\n    new_session_id = str(uuid.uuid4())\n    self._sessions[new_session_id] = {\n        \"created_at\": time.time(),\n        \"last_activity\": time.time(),\n    }\n```\n\nA cleanup method exists:\n\n```python\ndef _cleanup_sessions(self) -\u003e None:\n    now = time.time()\n    expired = [sid for sid, data in self._sessions.items()\n               if now - data[\"last_activity\"] \u003e self.session_ttl]\n    for sid in expired:\n        del self._sessions[sid]\n```\n\nbut grep across the package shows it has no call sites: it is never invoked on a timer, on request handling, or from any background task. self.session_ttl (default 3600) is stored and otherwise unused. There is no maximum-session check anywhere on the write path. As a result self._sessions grows monotonically for the lifetime of the process.\n\ninitialize is unauthenticated: in mcp_post the API-key check is skipped when no key is configured (the default), and initialize does not require a prior session. The Origin check is the only gate, and a request with no Origin header is allowed; additionally the Origin allowlist is bypassable (see the companion report on the startswith Origin-validation bypass), so the endpoint is reachable from a malicious web page as well as directly.\n\nThe server-side cancellation set in server.py has the same defect:\n\n```python\nif method == \"notifications/cancelled\":\n    request_id = params.get(\"requestId\")\n    if request_id:\n        self._cancelled_requests.add(str(request_id))   # never cleared\n```\n\nself._cancelled_requests is an unbounded set that is added to but never pruned.\n\n### PoC\n\nscripts/poc_mcp_session_dos.sh. Start the server (default config, no API key):\n\n```\npraisonai mcp serve --transport http-stream --host 127.0.0.1 --port 8080\n```\n\nSend repeated initialize requests and watch the active session count grow:\n\n```bash\nfor i in $(seq 1 200); do\n  curl -s -o /dev/null -X POST http://127.0.0.1:8080/mcp \\\n    -H \u0027Content-Type: application/json\u0027 -H \u0027Origin: http://localhost\u0027 \\\n    -d \u0027{\"jsonrpc\":\"2.0\",\"id\":1,\"method\":\"initialize\",\"params\":{\"protocolVersion\":\"2025-06-18\",\"capabilities\":{},\"clientInfo\":{\"name\":\"x\",\"version\":\"1\"}}}\u0027\ndone\ncurl -s http://127.0.0.1:8080/health\n```\n\nObserved on 4.6.52 after 200 requests:\n\n```\n{\"status\":\"healthy\",\"server\":\"praisonai\",\"version\":\"1.0.0\",\"protocol_version\":\"2025-11-25\",\"active_sessions\":200}\n```\n\nThe count rises by one per request and never decreases; there is no TTL expiry and no cap. Sustained requests grow the process resident set without bound. Each session also retains any SSE event history keyed by session id, amplifying the per-session footprint.\n\n### Impact\n\nAn unauthenticated client can exhaust the memory of the host running the MCP server, leading to denial of service (the process is terminated by the OOM killer, taking down the agent endpoint). When the server is bound to a routable interface (for example --host 0.0.0.0, common in containers), this is a direct remote unauthenticated DoS. With the default localhost bind, it is reachable from any web page the operator visits, because initialize is unauthenticated and the Origin gate is bypassable. The defect is a missing cleanup wiring plus the absence of any session cap, so it manifests even under benign long-running use.\n\n### Remediation\n\nEnforce the session TTL and cap the number of concurrent sessions: call _cleanup_sessions periodically (a background asyncio task, or opportunistically on each request) and reject new sessions with a 429/503 once a configurable maximum is reached. Bound _cancelled_requests similarly (for example an LRU or a periodic prune keyed by age), since it is also never cleared. Require authentication by default on the HTTP-stream transport so that anonymous clients cannot create sessions at all.",
  "id": "GHSA-wv94-5qcp-6m36",
  "modified": "2026-08-25T14:34:28Z",
  "published": "2026-08-25T14:34:28Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/MervinPraison/PraisonAI/security/advisories/GHSA-wv94-5qcp-6m36"
    },
    {
      "type": "WEB",
      "url": "https://github.com/MervinPraison/PraisonAI/commit/2f9677abb2ea68eab864ee8b6a828fd0141612e1"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/MervinPraison/PraisonAI"
    },
    {
      "type": "WEB",
      "url": "https://github.com/MervinPraison/PraisonAI/releases/tag/v4.6.58"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H",
      "type": "CVSS_V3"
    }
  ],
  "summary": "PraisonAI MCP HTTP server has unauthenticated unbounded session accumulation (memory exhaustion; session TTL never enforced)"
}

PYSEC-2026-3897

Vulnerability from pysec - Published: 2026-09-10 09:44 - Updated: 2026-09-10 11:02

Details

Summary

Details

In transports/http_stream.py, each initialize creates and stores a session with no limit:

if body.get("method") == "initialize":
    new_session_id = str(uuid.uuid4())
    self._sessions[new_session_id] = {
        "created_at": time.time(),
        "last_activity": time.time(),
    }

A cleanup method exists:

def _cleanup_sessions(self) -> None:
    now = time.time()
    expired = [sid for sid, data in self._sessions.items()
               if now - data["last_activity"] > self.session_ttl]
    for sid in expired:
        del self._sessions[sid]

The server-side cancellation set in server.py has the same defect:

if method == "notifications/cancelled":
    request_id = params.get("requestId")
    if request_id:
        self._cancelled_requests.add(str(request_id))   # never cleared

self._cancelled_requests is an unbounded set that is added to but never pruned.

PoC

scripts/poc_mcp_session_dos.sh. Start the server (default config, no API key):

praisonai mcp serve --transport http-stream --host 127.0.0.1 --port 8080

Send repeated initialize requests and watch the active session count grow:

for i in $(seq 1 200); do
  curl -s -o /dev/null -X POST http://127.0.0.1:8080/mcp \
    -H 'Content-Type: application/json' -H 'Origin: http://localhost' \
    -d '{"jsonrpc":"2.0","id":1,"method":"initialize","params":{"protocolVersion":"2025-06-18","capabilities":{},"clientInfo":{"name":"x","version":"1"}}}'
done
curl -s http://127.0.0.1:8080/health

Observed on 4.6.52 after 200 requests:

{"status":"healthy","server":"praisonai","version":"1.0.0","protocol_version":"2025-11-25","active_sessions":200}

Impact

Remediation

Severity

6.5 (Medium)


                  
                    CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H

Impacted products

Name	purl
praisonai	pkg:pypi/praisonai

Aliases

JSON

To clipboard

{
  "affected": [
    {
      "package": {
        "ecosystem": "PyPI",
        "name": "praisonai",
        "purl": "pkg:pypi/praisonai"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "4.6.58"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "0.0.1",
        "0.0.10",
        "0.0.11",
        "0.0.12",
        "0.0.13",
        "0.0.14",
        "0.0.15",
        "0.0.16",
        "0.0.17",
        "0.0.18",
        "0.0.19",
        "0.0.2",
        "0.0.20",
        "0.0.21",
        "0.0.22",
        "0.0.23",
        "0.0.24",
        "0.0.25",
        "0.0.26",
        "0.0.27",
        "0.0.28",
        "0.0.29",
        "0.0.3",
        "0.0.30",
        "0.0.31",
        "0.0.32",
        "0.0.33",
        "0.0.34",
        "0.0.35",
        "0.0.36",
        "0.0.37",
        "0.0.38",
        "0.0.39",
        "0.0.4",
        "0.0.40",
        "0.0.41",
        "0.0.42",
        "0.0.43",
        "0.0.44",
        "0.0.45",
        "0.0.46",
        "0.0.47",
        "0.0.48",
        "0.0.49",
        "0.0.5",
        "0.0.50",
        "0.0.52",
        "0.0.53",
        "0.0.54",
        "0.0.55",
        "0.0.56",
        "0.0.57",
        "0.0.58",
        "0.0.59",
        "0.0.59rc11",
        "0.0.59rc2",
        "0.0.59rc3",
        "0.0.59rc5",
        "0.0.59rc6",
        "0.0.59rc7",
        "0.0.59rc8",
        "0.0.59rc9",
        "0.0.6",
        "0.0.61",
        "0.0.64",
        "0.0.65",
        "0.0.66",
        "0.0.67",
        "0.0.68",
        "0.0.69",
        "0.0.7",
        "0.0.70",
        "0.0.71",
        "0.0.72",
        "0.0.73",
        "0.0.74",
        "0.0.8",
        "0.0.9",
        "0.1.0",
        "0.1.1",
        "0.1.10",
        "0.1.2",
        "0.1.3",
        "0.1.4",
        "0.1.5",
        "0.1.6",
        "0.1.7",
        "0.1.8",
        "0.1.9",
        "1.0.0",
        "1.0.1",
        "1.0.10",
        "1.0.11",
        "1.0.2",
        "1.0.3",
        "1.0.4",
        "1.0.5",
        "1.0.6",
        "1.0.8",
        "1.0.9",
        "2.0.0",
        "2.0.1",
        "2.0.10",
        "2.0.11",
        "2.0.12",
        "2.0.13",
        "2.0.14",
        "2.0.15",
        "2.0.16",
        "2.0.17",
        "2.0.18",
        "2.0.19",
        "2.0.2",
        "2.0.20",
        "2.0.22",
        "2.0.23",
        "2.0.24",
        "2.0.25",
        "2.0.26",
        "2.0.27",
        "2.0.28",
        "2.0.29",
        "2.0.3",
        "2.0.30",
        "2.0.31",
        "2.0.32",
        "2.0.33",
        "2.0.34",
        "2.0.35",
        "2.0.36",
        "2.0.37",
        "2.0.38",
        "2.0.39",
        "2.0.40",
        "2.0.41",
        "2.0.42",
        "2.0.43",
        "2.0.44",
        "2.0.45",
        "2.0.46",
        "2.0.47",
        "2.0.48",
        "2.0.49",
        "2.0.5",
        "2.0.50",
        "2.0.51",
        "2.0.53",
        "2.0.54",
        "2.0.55",
        "2.0.56",
        "2.0.57",
        "2.0.58",
        "2.0.59",
        "2.0.6",
        "2.0.60",
        "2.0.61",
        "2.0.62",
        "2.0.63",
        "2.0.64",
        "2.0.65",
        "2.0.66",
        "2.0.67",
        "2.0.68",
        "2.0.69",
        "2.0.7",
        "2.0.70",
        "2.0.71",
        "2.0.72",
        "2.0.73",
        "2.0.74",
        "2.0.75",
        "2.0.76",
        "2.0.77",
        "2.0.78",
        "2.0.79",
        "2.0.8",
        "2.0.80",
        "2.0.81",
        "2.0.9",
        "2.1.0",
        "2.1.1",
        "2.1.4",
        "2.1.5",
        "2.1.6",
        "2.2.1",
        "2.2.10",
        "2.2.11",
        "2.2.12",
        "2.2.13",
        "2.2.14",
        "2.2.15",
        "2.2.16",
        "2.2.17",
        "2.2.18",
        "2.2.19",
        "2.2.2",
        "2.2.20",
        "2.2.21",
        "2.2.22",
        "2.2.24",
        "2.2.25",
        "2.2.26",
        "2.2.27",
        "2.2.28",
        "2.2.29",
        "2.2.3",
        "2.2.30",
        "2.2.31",
        "2.2.32",
        "2.2.33",
        "2.2.34",
        "2.2.35",
        "2.2.36",
        "2.2.37",
        "2.2.38",
        "2.2.39",
        "2.2.4",
        "2.2.40",
        "2.2.41",
        "2.2.42",
        "2.2.43",
        "2.2.44",
        "2.2.45",
        "2.2.46",
        "2.2.47",
        "2.2.48",
        "2.2.49",
        "2.2.5",
        "2.2.50",
        "2.2.51",
        "2.2.52",
        "2.2.53",
        "2.2.54",
        "2.2.55",
        "2.2.56",
        "2.2.57",
        "2.2.58",
        "2.2.59",
        "2.2.6",
        "2.2.60",
        "2.2.61",
        "2.2.62",
        "2.2.63",
        "2.2.64",
        "2.2.65",
        "2.2.66",
        "2.2.67",
        "2.2.68",
        "2.2.69",
        "2.2.7",
        "2.2.70",
        "2.2.71",
        "2.2.72",
        "2.2.73",
        "2.2.74",
        "2.2.75",
        "2.2.76",
        "2.2.77",
        "2.2.78",
        "2.2.79",
        "2.2.8",
        "2.2.80",
        "2.2.81",
        "2.2.82",
        "2.2.83",
        "2.2.84",
        "2.2.86",
        "2.2.87",
        "2.2.88",
        "2.2.89",
        "2.2.9",
        "2.2.90",
        "2.2.91",
        "2.2.93",
        "2.2.95",
        "2.2.96",
        "2.2.97",
        "2.2.98",
        "2.2.99",
        "2.3.0",
        "2.3.1",
        "2.3.10",
        "2.3.11",
        "2.3.12",
        "2.3.13",
        "2.3.14",
        "2.3.15",
        "2.3.16",
        "2.3.18",
        "2.3.19",
        "2.3.2",
        "2.3.20",
        "2.3.21",
        "2.3.22",
        "2.3.23",
        "2.3.24",
        "2.3.25",
        "2.3.26",
        "2.3.27",
        "2.3.28",
        "2.3.29",
        "2.3.3",
        "2.3.30",
        "2.3.31",
        "2.3.32",
        "2.3.33",
        "2.3.34",
        "2.3.35",
        "2.3.36",
        "2.3.37",
        "2.3.38",
        "2.3.39",
        "2.3.4",
        "2.3.40",
        "2.3.41",
        "2.3.42",
        "2.3.43",
        "2.3.44",
        "2.3.45",
        "2.3.46",
        "2.3.47",
        "2.3.48",
        "2.3.49",
        "2.3.5",
        "2.3.50",
        "2.3.51",
        "2.3.52",
        "2.3.53",
        "2.3.54",
        "2.3.55",
        "2.3.56",
        "2.3.57",
        "2.3.58",
        "2.3.59",
        "2.3.6",
        "2.3.60",
        "2.3.61",
        "2.3.62",
        "2.3.63",
        "2.3.64",
        "2.3.65",
        "2.3.66",
        "2.3.67",
        "2.3.68",
        "2.3.69",
        "2.3.7",
        "2.3.70",
        "2.3.71",
        "2.3.72",
        "2.3.73",
        "2.3.74",
        "2.3.75",
        "2.3.76",
        "2.3.77",
        "2.3.78",
        "2.3.79",
        "2.3.8",
        "2.3.80",
        "2.3.81",
        "2.3.82",
        "2.3.83",
        "2.3.84",
        "2.3.85",
        "2.3.86",
        "2.3.87",
        "2.3.9",
        "2.4.0",
        "2.4.1",
        "2.4.2",
        "2.4.3",
        "2.4.4",
        "2.5.0",
        "2.5.1",
        "2.5.2",
        "2.5.3",
        "2.5.4",
        "2.5.5",
        "2.5.6",
        "2.5.7",
        "2.6.0",
        "2.6.1",
        "2.6.2",
        "2.6.3",
        "2.6.4",
        "2.6.5",
        "2.6.6",
        "2.6.7",
        "2.6.8",
        "2.7.0",
        "2.8.3",
        "2.8.4",
        "2.8.5",
        "2.8.6",
        "2.8.7",
        "2.8.8",
        "2.8.9",
        "2.9.0",
        "2.9.1",
        "2.9.2",
        "3.0.0",
        "3.0.1",
        "3.0.2",
        "3.0.3",
        "3.0.4",
        "3.0.5",
        "3.0.6",
        "3.0.7",
        "3.0.8",
        "3.0.9",
        "3.1.0",
        "3.1.1",
        "3.1.2",
        "3.1.3",
        "3.1.4",
        "3.1.5",
        "3.1.6",
        "3.1.7",
        "3.1.8",
        "3.1.9",
        "3.10.0",
        "3.10.1",
        "3.10.10",
        "3.10.11",
        "3.10.12",
        "3.10.13",
        "3.10.14",
        "3.10.15",
        "3.10.16",
        "3.10.17",
        "3.10.18",
        "3.10.19",
        "3.10.2",
        "3.10.20",
        "3.10.21",
        "3.10.22",
        "3.10.23",
        "3.10.24",
        "3.10.25",
        "3.10.26",
        "3.10.27",
        "3.10.3",
        "3.10.4",
        "3.10.5",
        "3.10.6",
        "3.10.7",
        "3.10.8",
        "3.10.9",
        "3.11.0",
        "3.11.1",
        "3.11.10",
        "3.11.11",
        "3.11.12",
        "3.11.13",
        "3.11.14",
        "3.11.2",
        "3.11.3",
        "3.11.4",
        "3.11.8",
        "3.11.9",
        "3.12.0",
        "3.12.1",
        "3.12.2",
        "3.12.3",
        "3.2.0",
        "3.2.1",
        "3.3.0",
        "3.3.1",
        "3.4.0",
        "3.4.1",
        "3.5.0",
        "3.5.1",
        "3.5.2",
        "3.5.3",
        "3.5.4",
        "3.5.5",
        "3.5.6",
        "3.5.7",
        "3.5.8",
        "3.5.9",
        "3.6.0",
        "3.6.1",
        "3.6.2",
        "3.7.0",
        "3.7.1",
        "3.7.2",
        "3.7.3",
        "3.7.4",
        "3.7.5",
        "3.7.6",
        "3.7.7",
        "3.7.8",
        "3.7.9",
        "3.8.0",
        "3.8.1",
        "3.8.10",
        "3.8.11",
        "3.8.12",
        "3.8.13",
        "3.8.14",
        "3.8.16",
        "3.8.17",
        "3.8.18",
        "3.8.19",
        "3.8.2",
        "3.8.20",
        "3.8.21",
        "3.8.22",
        "3.8.3",
        "3.8.4",
        "3.8.5",
        "3.8.6",
        "3.8.7",
        "3.8.8",
        "3.8.9",
        "3.9.0",
        "3.9.1",
        "3.9.10",
        "3.9.11",
        "3.9.12",
        "3.9.13",
        "3.9.14",
        "3.9.15",
        "3.9.16",
        "3.9.17",
        "3.9.18",
        "3.9.19",
        "3.9.2",
        "3.9.20",
        "3.9.21",
        "3.9.22",
        "3.9.23",
        "3.9.24",
        "3.9.25",
        "3.9.26",
        "3.9.27",
        "3.9.28",
        "3.9.29",
        "3.9.3",
        "3.9.30",
        "3.9.31",
        "3.9.32",
        "3.9.33",
        "3.9.34",
        "3.9.35",
        "3.9.4",
        "3.9.5",
        "3.9.6",
        "3.9.7",
        "3.9.8",
        "3.9.9",
        "4.0.0",
        "4.1.0",
        "4.2.0",
        "4.2.1",
        "4.2.2",
        "4.2.3",
        "4.2.4",
        "4.3.0",
        "4.3.1",
        "4.4.0",
        "4.4.10",
        "4.4.11",
        "4.4.12",
        "4.4.2",
        "4.4.3",
        "4.4.4",
        "4.4.5",
        "4.4.6",
        "4.4.7",
        "4.4.8",
        "4.4.9",
        "4.5.0",
        "4.5.1",
        "4.5.10",
        "4.5.100",
        "4.5.101",
        "4.5.102",
        "4.5.103",
        "4.5.104",
        "4.5.105",
        "4.5.106",
        "4.5.107",
        "4.5.108",
        "4.5.109",
        "4.5.11",
        "4.5.110",
        "4.5.111",
        "4.5.112",
        "4.5.113",
        "4.5.114",
        "4.5.115",
        "4.5.117",
        "4.5.118",
        "4.5.119",
        "4.5.12",
        "4.5.120",
        "4.5.121",
        "4.5.122",
        "4.5.123",
        "4.5.124",
        "4.5.125",
        "4.5.126",
        "4.5.127",
        "4.5.128",
        "4.5.129",
        "4.5.13",
        "4.5.130",
        "4.5.131",
        "4.5.132",
        "4.5.133",
        "4.5.134",
        "4.5.135",
        "4.5.136",
        "4.5.137",
        "4.5.139",
        "4.5.14",
        "4.5.140",
        "4.5.143",
        "4.5.144",
        "4.5.145",
        "4.5.149",
        "4.5.15",
        "4.5.16",
        "4.5.18",
        "4.5.19",
        "4.5.2",
        "4.5.20",
        "4.5.21",
        "4.5.22",
        "4.5.23",
        "4.5.24",
        "4.5.25",
        "4.5.26",
        "4.5.27",
        "4.5.28",
        "4.5.29",
        "4.5.3",
        "4.5.30",
        "4.5.31",
        "4.5.32",
        "4.5.33",
        "4.5.34",
        "4.5.35",
        "4.5.36",
        "4.5.37",
        "4.5.38",
        "4.5.39",
        "4.5.40",
        "4.5.41",
        "4.5.42",
        "4.5.43",
        "4.5.44",
        "4.5.45",
        "4.5.46",
        "4.5.48",
        "4.5.49",
        "4.5.5",
        "4.5.51",
        "4.5.52",
        "4.5.54",
        "4.5.55",
        "4.5.56",
        "4.5.57",
        "4.5.58",
        "4.5.59",
        "4.5.6",
        "4.5.60",
        "4.5.62",
        "4.5.63",
        "4.5.64",
        "4.5.65",
        "4.5.67",
        "4.5.68",
        "4.5.69",
        "4.5.7",
        "4.5.70",
        "4.5.71",
        "4.5.72",
        "4.5.73",
        "4.5.74",
        "4.5.76",
        "4.5.77",
        "4.5.78",
        "4.5.79",
        "4.5.8",
        "4.5.80",
        "4.5.81",
        "4.5.82",
        "4.5.83",
        "4.5.85",
        "4.5.87",
        "4.5.88",
        "4.5.89",
        "4.5.9",
        "4.5.90",
        "4.5.93",
        "4.5.94",
        "4.5.95",
        "4.5.96",
        "4.5.97",
        "4.5.98",
        "4.6.10",
        "4.6.11",
        "4.6.12",
        "4.6.13",
        "4.6.14",
        "4.6.15",
        "4.6.16",
        "4.6.18",
        "4.6.19",
        "4.6.20",
        "4.6.21",
        "4.6.22",
        "4.6.23",
        "4.6.24",
        "4.6.25",
        "4.6.26",
        "4.6.27",
        "4.6.28",
        "4.6.29",
        "4.6.30",
        "4.6.31",
        "4.6.32",
        "4.6.33",
        "4.6.34",
        "4.6.35",
        "4.6.36",
        "4.6.37",
        "4.6.38",
        "4.6.39",
        "4.6.40",
        "4.6.41",
        "4.6.42",
        "4.6.43",
        "4.6.44",
        "4.6.45",
        "4.6.46",
        "4.6.47",
        "4.6.48",
        "4.6.50",
        "4.6.51",
        "4.6.52",
        "4.6.53",
        "4.6.54",
        "4.6.55",
        "4.6.56",
        "4.6.57",
        "4.6.9"
      ]
    }
  ],
  "aliases": [
    "CVE-2026-55531",
    "GHSA-wv94-5qcp-6m36"
  ],
  "details": "### Summary\n\nThe PraisonAI MCP HTTP-stream server creates a new in-memory session on every initialize request and never removes it. The cleanup routine that would expire sessions (_cleanup_sessions) is defined but never called anywhere in the codebase, and the configured session TTL is never enforced. There is no cap on the number of sessions. Because initialize requires no authentication and the server keeps every session dictionary forever, an attacker who can reach the endpoint (directly when the server is bound to a routable address, or from a victim\u0027s browser via the separate Origin-validation bypass) can drive memory usage up without bound until the process is killed by the out-of-memory killer. The same unbounded-growth pattern also applies to the cancelled-requests set populated by notifications/cancelled.\n\n### Details\n\nIn transports/http_stream.py, each initialize creates and stores a session with no limit:\n\n```python\nif body.get(\"method\") == \"initialize\":\n    new_session_id = str(uuid.uuid4())\n    self._sessions[new_session_id] = {\n        \"created_at\": time.time(),\n        \"last_activity\": time.time(),\n    }\n```\n\nA cleanup method exists:\n\n```python\ndef _cleanup_sessions(self) -\u003e None:\n    now = time.time()\n    expired = [sid for sid, data in self._sessions.items()\n               if now - data[\"last_activity\"] \u003e self.session_ttl]\n    for sid in expired:\n        del self._sessions[sid]\n```\n\nbut grep across the package shows it has no call sites: it is never invoked on a timer, on request handling, or from any background task. self.session_ttl (default 3600) is stored and otherwise unused. There is no maximum-session check anywhere on the write path. As a result self._sessions grows monotonically for the lifetime of the process.\n\ninitialize is unauthenticated: in mcp_post the API-key check is skipped when no key is configured (the default), and initialize does not require a prior session. The Origin check is the only gate, and a request with no Origin header is allowed; additionally the Origin allowlist is bypassable (see the companion report on the startswith Origin-validation bypass), so the endpoint is reachable from a malicious web page as well as directly.\n\nThe server-side cancellation set in server.py has the same defect:\n\n```python\nif method == \"notifications/cancelled\":\n    request_id = params.get(\"requestId\")\n    if request_id:\n        self._cancelled_requests.add(str(request_id))   # never cleared\n```\n\nself._cancelled_requests is an unbounded set that is added to but never pruned.\n\n### PoC\n\nscripts/poc_mcp_session_dos.sh. Start the server (default config, no API key):\n\n```\npraisonai mcp serve --transport http-stream --host 127.0.0.1 --port 8080\n```\n\nSend repeated initialize requests and watch the active session count grow:\n\n```bash\nfor i in $(seq 1 200); do\n  curl -s -o /dev/null -X POST http://127.0.0.1:8080/mcp \\\n    -H \u0027Content-Type: application/json\u0027 -H \u0027Origin: http://localhost\u0027 \\\n    -d \u0027{\"jsonrpc\":\"2.0\",\"id\":1,\"method\":\"initialize\",\"params\":{\"protocolVersion\":\"2025-06-18\",\"capabilities\":{},\"clientInfo\":{\"name\":\"x\",\"version\":\"1\"}}}\u0027\ndone\ncurl -s http://127.0.0.1:8080/health\n```\n\nObserved on 4.6.52 after 200 requests:\n\n```\n{\"status\":\"healthy\",\"server\":\"praisonai\",\"version\":\"1.0.0\",\"protocol_version\":\"2025-11-25\",\"active_sessions\":200}\n```\n\nThe count rises by one per request and never decreases; there is no TTL expiry and no cap. Sustained requests grow the process resident set without bound. Each session also retains any SSE event history keyed by session id, amplifying the per-session footprint.\n\n### Impact\n\nAn unauthenticated client can exhaust the memory of the host running the MCP server, leading to denial of service (the process is terminated by the OOM killer, taking down the agent endpoint). When the server is bound to a routable interface (for example --host 0.0.0.0, common in containers), this is a direct remote unauthenticated DoS. With the default localhost bind, it is reachable from any web page the operator visits, because initialize is unauthenticated and the Origin gate is bypassable. The defect is a missing cleanup wiring plus the absence of any session cap, so it manifests even under benign long-running use.\n\n### Remediation\n\nEnforce the session TTL and cap the number of concurrent sessions: call _cleanup_sessions periodically (a background asyncio task, or opportunistically on each request) and reject new sessions with a 429/503 once a configurable maximum is reached. Bound _cancelled_requests similarly (for example an LRU or a periodic prune keyed by age), since it is also never cleared. Require authentication by default on the HTTP-stream transport so that anonymous clients cannot create sessions at all.",
  "id": "PYSEC-2026-3897",
  "modified": "2026-09-10T11:02:27.806145Z",
  "published": "2026-09-10T09:44:54.136697Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/MervinPraison/PraisonAI/security/advisories/GHSA-wv94-5qcp-6m36"
    },
    {
      "type": "WEB",
      "url": "https://github.com/MervinPraison/PraisonAI/commit/2f9677abb2ea68eab864ee8b6a828fd0141612e1"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/MervinPraison/PraisonAI"
    },
    {
      "type": "WEB",
      "url": "https://github.com/MervinPraison/PraisonAI/releases/tag/v4.6.58"
    },
    {
      "type": "PACKAGE",
      "url": "https://pypi.org/project/praisonai"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/advisories/GHSA-wv94-5qcp-6m36"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-55531"
    }
  ],
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H",
      "type": "CVSS_V3"
    }
  ],
  "summary": "PraisonAI MCP HTTP server has unauthenticated unbounded session accumulation (memory exhaustion; session TTL never enforced)"
}

Sightings

Author	Source	Type	Date	Other

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

Vulnerability timeline

Sightings and recorded dates, grouped by day · UTC

Order JSON

Publication & reservation Sightings KEV catalogs Other timestamps

Loading timeline…

The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.

Related by attack behaviour

Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.

Action not permitted

CVE-2026-55531 (GCVE-0-2026-55531)

FKIE_CVE-2026-55531

GHSA-WV94-5QCP-6M36

Summary

Details

PoC

Impact

Remediation

PYSEC-2026-3897

Summary

Details

PoC

Impact

Remediation

Tags

Sightings

Nomenclature

Vulnerability timeline

Related by attack behaviour