Vulnerability-Lookup

CVE-2026-77265 (GCVE-0-2026-77265)

Vulnerability from cvelistv5 – Published: 2026-09-22 17:47 – Updated: 2026-09-28 17:46

Title

MCP Atlassian: SSRF via DNS Rebinding in Header-Based Authentication Flow

Summary

MCP Atlassian is a Model Context Protocol (MCP) server for Atlassian products (Confluence and Jira). Prior to 0.22.0, header-supplied Jira or Confluence URLs are resolved and validated before the HTTP client resolves the hostname again for the connection. An unauthenticated caller can use a DNS-rebinding hostname that returns a public address during validation and an internal address during connection, causing requests to internal or metadata services. The advisory traces the vulnerable input and processing flow through X-Atlassian-Jira-Url, X-Atlassian-Confluence-Url, validate_url_for_ssrf, and DNS rebinding, which identify the affected entry points, controls, and code paths. This issue is fixed in version 0.22.0.

Severity

5.9 (Medium)


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

SSVC

Exploitation: poc Automatable: no Technical Impact: partial

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-09-28 17:46 UTC

CWE

CWE-918 - Server-Side Request Forgery (SSRF)

Assigner

GitHub_M mitre root Scorecard

References

4 references

URL	Tags
https://github.com/sooperset/mcp-atlassian/securi…	x_refsource_CONFIRM
https://github.com/sooperset/mcp-atlassian/pull/1448	x_refsource_MISC
https://github.com/sooperset/mcp-atlassian/commit…	x_refsource_MISC
https://github.com/sooperset/mcp-atlassian/releas…	x_refsource_MISC

Impacted products

1 product

Vendor	Product	Version	CPE status
sooperset	mcp-atlassian	Affected: < 0.22.0	guessed

Show details on NVD website

JSON

To clipboard

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FKIE_CVE-2026-77265

Vulnerability from fkie_nvd - Published: 2026-09-22 18:17 - Updated: 2026-09-29 19:00

Severity

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

Summary

References

URL	Tags
security-advisories@github.com	https://github.com/sooperset/mcp-atlassian/commit/b041733473f95119dd539542a43c280737a8e460	Patch
security-advisories@github.com	https://github.com/sooperset/mcp-atlassian/pull/1448	Issue Tracking, Patch
security-advisories@github.com	https://github.com/sooperset/mcp-atlassian/releases/tag/v0.22.0	Release Notes
security-advisories@github.com	https://github.com/sooperset/mcp-atlassian/security/advisories/GHSA-49xv-9743-pw8w	Exploit, Vendor Advisory
134c704f-9b21-4f2e-91b3-4a467353bcc0	https://github.com/sooperset/mcp-atlassian/security/advisories/GHSA-49xv-9743-pw8w	Exploit, Vendor Advisory

Impacted products

	Vendor	Product	Version
	mcp-atlassian	mcp_atlassian	*

JSON

To clipboard

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        "Issue Tracking",
        "Patch"
      ],
      "url": "https://github.com/sooperset/mcp-atlassian/pull/1448"
    },
    {
      "source": "security-advisories@github.com",
      "tags": [
        "Release Notes"
      ],
      "url": "https://github.com/sooperset/mcp-atlassian/releases/tag/v0.22.0"
    },
    {
      "source": "security-advisories@github.com",
      "tags": [
        "Exploit",
        "Vendor Advisory"
      ],
      "url": "https://github.com/sooperset/mcp-atlassian/security/advisories/GHSA-49xv-9743-pw8w"
    },
    {
      "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
      "tags": [
        "Exploit",
        "Vendor Advisory"
      ],
      "url": "https://github.com/sooperset/mcp-atlassian/security/advisories/GHSA-49xv-9743-pw8w"
    }
  ],
  "sourceIdentifier": "security-advisories@github.com",
  "vulnStatus": "Analyzed",
  "weaknesses": [
    {
      "description": [
        {
          "lang": "en",
          "value": "CWE-918"
        }
      ],
      "source": "security-advisories@github.com",
      "type": "Secondary"
    }
  ]
}

GHSA-49XV-9743-PW8W

Vulnerability from github – Published: 2026-09-22 20:35 – Updated: 2026-09-22 20:35

Summary

MCP Atlassian: SSRF via DNS Rebinding in Header-Based Authentication Flow

Details

Summary

The SSRF protection for header-based authentication uses a validate-then-use pattern vulnerable to DNS rebinding. validate_url_for_ssrf resolves the hostname via DNS and checks that the resolved IP is globally routable. However, the actual HTTP request happens later, during which the DNS record may have changed to point to an internal IP (127.0.0.1, 169.254.169.254, etc.). The SSRF redirect hook only validates redirect targets, not the initial connection.

Details

The vulnerability spans main.py (validation) and dependencies.py (use).

Step 1 -- URL validation at middleware time:

In src/mcp_atlassian/servers/main.py:524-531, the URL from X-Atlassian-Jira-Url is validated:

if jira_url_str:
    ssrf_error = validate_url_for_ssrf(jira_url_str)
    if ssrf_error:
        # blocked

validate_url_for_ssrf (src/mcp_atlassian/utils/urls.py:113-116) resolves DNS and checks is_global:

dns_error = _check_dns_resolution(hostname)
if dns_error:
    return dns_error

Step 2 -- HTTP request happens later with a separate DNS resolution:

In src/mcp_atlassian/servers/dependencies.py:544-562, a JiraFetcher is created with the attacker URL and makes HTTP requests to it. The SSRF redirect hook (attach_ssrf_hook=True) is applied but only checks redirect Location headers, not the initial connection target.

DNS rebinding timeline:

Attacker sets up rebind.attacker.com with short TTL (1 second)
First DNS resolution (validate_url_for_ssrf): returns 1.2.3.4 (public) -- passes
TTL expires
Second DNS resolution (requests.get): returns 169.254.169.254 (metadata)
HTTP request reaches internal IP, bypassing the SSRF check

PoC

Use a DNS rebinding service like rbndr.us. Send a request with X-Atlassian-Jira-Url set to a rebinding hostname (e.g., rebind-169.254.169.254-1.2.3.4.rbndr.us) and X-Atlassian-Jira-Personal-Token set to any value. With approximately 50% probability per attempt, the request reaches the internal metadata service.

Impact

Cloud metadata access: Steal IAM credentials via 169.254.169.254
Internal network scanning: Proxy requests to internal services
AC:H: DNS rebinding is probabilistic and requires multiple attempts
Limited to header_pat branch: Only affects deployments accepting header-based PAT authentication

Recommended Fix

Pin DNS resolution: resolve the hostname once during validation, then connect to the resolved IP directly (with the original hostname in the Host header). This eliminates the TOCTOU gap between validation and use.

Severity

5.9 (Medium)


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

Show details on source website

JSON

To clipboard

{
  "affected": [
    {
      "package": {
        "ecosystem": "PyPI",
        "name": "mcp-atlassian"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "0.22.0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-77265"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-918"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-09-22T20:35:08Z",
    "nvd_published_at": "2026-09-22T18:17:18Z",
    "severity": "MODERATE"
  },
  "details": "## Summary\n\nThe SSRF protection for header-based authentication uses a validate-then-use pattern vulnerable to DNS rebinding. validate_url_for_ssrf resolves the hostname via DNS and checks that the resolved IP is globally routable. However, the actual HTTP request happens later, during which the DNS record may have changed to point to an internal IP (127.0.0.1, 169.254.169.254, etc.). The SSRF redirect hook only validates redirect targets, not the initial connection.\n\n## Details\n\nThe vulnerability spans main.py (validation) and dependencies.py (use).\n\n**Step 1 -- URL validation at middleware time:**\n\nIn src/mcp_atlassian/servers/main.py:524-531, the URL from X-Atlassian-Jira-Url is validated:\n\n    if jira_url_str:\n        ssrf_error = validate_url_for_ssrf(jira_url_str)\n        if ssrf_error:\n            # blocked\n\nvalidate_url_for_ssrf (src/mcp_atlassian/utils/urls.py:113-116) resolves DNS and checks is_global:\n\n    dns_error = _check_dns_resolution(hostname)\n    if dns_error:\n        return dns_error\n\n**Step 2 -- HTTP request happens later with a separate DNS resolution:**\n\nIn src/mcp_atlassian/servers/dependencies.py:544-562, a JiraFetcher is created with the attacker URL and makes HTTP requests to it. The SSRF redirect hook (attach_ssrf_hook=True) is applied but only checks redirect Location headers, not the initial connection target.\n\n**DNS rebinding timeline:**\n\n1. Attacker sets up rebind.attacker.com with short TTL (1 second)\n2. First DNS resolution (validate_url_for_ssrf): returns 1.2.3.4 (public) -- passes\n3. TTL expires\n4. Second DNS resolution (requests.get): returns 169.254.169.254 (metadata)\n5. HTTP request reaches internal IP, bypassing the SSRF check\n\n## PoC\n\nUse a DNS rebinding service like rbndr.us. Send a request with X-Atlassian-Jira-Url set to a rebinding hostname (e.g., rebind-169.254.169.254-1.2.3.4.rbndr.us) and X-Atlassian-Jira-Personal-Token set to any value. With approximately 50% probability per attempt, the request reaches the internal metadata service.\n\n## Impact\n\n- **Cloud metadata access**: Steal IAM credentials via 169.254.169.254\n- **Internal network scanning**: Proxy requests to internal services\n- **AC:H**: DNS rebinding is probabilistic and requires multiple attempts\n- **Limited to header_pat branch**: Only affects deployments accepting header-based PAT authentication\n\n## Recommended Fix\n\nPin DNS resolution: resolve the hostname once during validation, then connect to the resolved IP directly (with the original hostname in the Host header). This eliminates the TOCTOU gap between validation and use.",
  "id": "GHSA-49xv-9743-pw8w",
  "modified": "2026-09-22T20:35:08Z",
  "published": "2026-09-22T20:35:08Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/sooperset/mcp-atlassian/security/advisories/GHSA-49xv-9743-pw8w"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-77265"
    },
    {
      "type": "WEB",
      "url": "https://github.com/sooperset/mcp-atlassian/pull/1448"
    },
    {
      "type": "WEB",
      "url": "https://github.com/sooperset/mcp-atlassian/commit/b041733473f95119dd539542a43c280737a8e460"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/sooperset/mcp-atlassian"
    },
    {
      "type": "WEB",
      "url": "https://github.com/sooperset/mcp-atlassian/releases/tag/v0.22.0"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "MCP Atlassian: SSRF via DNS Rebinding in Header-Based Authentication Flow"
}

PYSEC-2026-4083

Vulnerability from pysec - Published: 2026-10-01 16:38 - Updated: 2026-10-01 17:10

Details

Summary

Details

The vulnerability spans main.py (validation) and dependencies.py (use).

Step 1 -- URL validation at middleware time:

In src/mcp_atlassian/servers/main.py:524-531, the URL from X-Atlassian-Jira-Url is validated:

if jira_url_str:
    ssrf_error = validate_url_for_ssrf(jira_url_str)
    if ssrf_error:
        # blocked

validate_url_for_ssrf (src/mcp_atlassian/utils/urls.py:113-116) resolves DNS and checks is_global:

dns_error = _check_dns_resolution(hostname)
if dns_error:
    return dns_error

Step 2 -- HTTP request happens later with a separate DNS resolution:

DNS rebinding timeline:

Attacker sets up rebind.attacker.com with short TTL (1 second)
First DNS resolution (validate_url_for_ssrf): returns 1.2.3.4 (public) -- passes
TTL expires
Second DNS resolution (requests.get): returns 169.254.169.254 (metadata)
HTTP request reaches internal IP, bypassing the SSRF check

PoC

Impact

Cloud metadata access: Steal IAM credentials via 169.254.169.254
Internal network scanning: Proxy requests to internal services
AC:H: DNS rebinding is probabilistic and requires multiple attempts
Limited to header_pat branch: Only affects deployments accepting header-based PAT authentication

Recommended Fix

Severity

5.9 (Medium)


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

Impacted products

Name	purl
mcp-atlassian	pkg:pypi/mcp-atlassian

Aliases

JSON

To clipboard

{
  "affected": [
    {
      "package": {
        "ecosystem": "PyPI",
        "name": "mcp-atlassian",
        "purl": "pkg:pypi/mcp-atlassian"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "0.22.0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "0.1.1",
        "0.1.10",
        "0.1.11",
        "0.1.12",
        "0.1.13",
        "0.1.14",
        "0.1.15",
        "0.1.16",
        "0.1.2",
        "0.1.3",
        "0.1.4",
        "0.1.6",
        "0.1.7",
        "0.1.8",
        "0.1.9",
        "0.10.0",
        "0.10.1",
        "0.10.2",
        "0.10.3",
        "0.10.4",
        "0.10.5",
        "0.10.6",
        "0.11.0",
        "0.11.1",
        "0.11.10",
        "0.11.11",
        "0.11.12",
        "0.11.2",
        "0.11.2a2",
        "0.11.3",
        "0.11.4",
        "0.11.5",
        "0.11.6",
        "0.11.7",
        "0.11.8",
        "0.11.9",
        "0.12.0",
        "0.13.0",
        "0.13.1",
        "0.14.0",
        "0.14.1",
        "0.14.2",
        "0.14.3",
        "0.15.0",
        "0.16.0",
        "0.16.1",
        "0.17.0",
        "0.18.0",
        "0.18.1",
        "0.19.0",
        "0.2.0",
        "0.2.1",
        "0.2.2",
        "0.2.3",
        "0.2.4",
        "0.2.5",
        "0.2.6",
        "0.20.0",
        "0.20.1",
        "0.21.0",
        "0.21.1",
        "0.3.0",
        "0.3.1",
        "0.4.0",
        "0.5.0",
        "0.6.0",
        "0.6.1",
        "0.6.2",
        "0.6.3",
        "0.6.4",
        "0.6.5",
        "0.7.0",
        "0.7.1",
        "0.8.0",
        "0.8.1",
        "0.8.2",
        "0.8.3",
        "0.8.4",
        "0.9.0"
      ]
    }
  ],
  "aliases": [
    "CVE-2026-77265",
    "GHSA-49xv-9743-pw8w"
  ],
  "details": "## Summary\n\nThe SSRF protection for header-based authentication uses a validate-then-use pattern vulnerable to DNS rebinding. validate_url_for_ssrf resolves the hostname via DNS and checks that the resolved IP is globally routable. However, the actual HTTP request happens later, during which the DNS record may have changed to point to an internal IP (127.0.0.1, 169.254.169.254, etc.). The SSRF redirect hook only validates redirect targets, not the initial connection.\n\n## Details\n\nThe vulnerability spans main.py (validation) and dependencies.py (use).\n\n**Step 1 -- URL validation at middleware time:**\n\nIn src/mcp_atlassian/servers/main.py:524-531, the URL from X-Atlassian-Jira-Url is validated:\n\n    if jira_url_str:\n        ssrf_error = validate_url_for_ssrf(jira_url_str)\n        if ssrf_error:\n            # blocked\n\nvalidate_url_for_ssrf (src/mcp_atlassian/utils/urls.py:113-116) resolves DNS and checks is_global:\n\n    dns_error = _check_dns_resolution(hostname)\n    if dns_error:\n        return dns_error\n\n**Step 2 -- HTTP request happens later with a separate DNS resolution:**\n\nIn src/mcp_atlassian/servers/dependencies.py:544-562, a JiraFetcher is created with the attacker URL and makes HTTP requests to it. The SSRF redirect hook (attach_ssrf_hook=True) is applied but only checks redirect Location headers, not the initial connection target.\n\n**DNS rebinding timeline:**\n\n1. Attacker sets up rebind.attacker.com with short TTL (1 second)\n2. First DNS resolution (validate_url_for_ssrf): returns 1.2.3.4 (public) -- passes\n3. TTL expires\n4. Second DNS resolution (requests.get): returns 169.254.169.254 (metadata)\n5. HTTP request reaches internal IP, bypassing the SSRF check\n\n## PoC\n\nUse a DNS rebinding service like rbndr.us. Send a request with X-Atlassian-Jira-Url set to a rebinding hostname (e.g., rebind-169.254.169.254-1.2.3.4.rbndr.us) and X-Atlassian-Jira-Personal-Token set to any value. With approximately 50% probability per attempt, the request reaches the internal metadata service.\n\n## Impact\n\n- **Cloud metadata access**: Steal IAM credentials via 169.254.169.254\n- **Internal network scanning**: Proxy requests to internal services\n- **AC:H**: DNS rebinding is probabilistic and requires multiple attempts\n- **Limited to header_pat branch**: Only affects deployments accepting header-based PAT authentication\n\n## Recommended Fix\n\nPin DNS resolution: resolve the hostname once during validation, then connect to the resolved IP directly (with the original hostname in the Host header). This eliminates the TOCTOU gap between validation and use.",
  "id": "PYSEC-2026-4083",
  "modified": "2026-10-01T17:10:30.040011Z",
  "published": "2026-10-01T16:38:35.564447Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/sooperset/mcp-atlassian/security/advisories/GHSA-49xv-9743-pw8w"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-77265"
    },
    {
      "type": "WEB",
      "url": "https://github.com/sooperset/mcp-atlassian/pull/1448"
    },
    {
      "type": "WEB",
      "url": "https://github.com/sooperset/mcp-atlassian/commit/b041733473f95119dd539542a43c280737a8e460"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/sooperset/mcp-atlassian"
    },
    {
      "type": "WEB",
      "url": "https://github.com/sooperset/mcp-atlassian/releases/tag/v0.22.0"
    },
    {
      "type": "PACKAGE",
      "url": "https://pypi.org/project/mcp-atlassian"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/advisories/GHSA-49xv-9743-pw8w"
    }
  ],
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "MCP Atlassian: SSRF via DNS Rebinding in Header-Based Authentication Flow"
}

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.

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-2026-77265 (GCVE-0-2026-77265)

FKIE_CVE-2026-77265

GHSA-49XV-9743-PW8W

Summary

Details

PoC

Impact

Recommended Fix

PYSEC-2026-4083

Summary

Details

PoC

Impact

Recommended Fix

Tags

Sightings

Nomenclature

Related by attack behaviour