Vulnerability-Lookup

GHSA-CQR9-F685-GR3W

Vulnerability from github – Published: 2026-10-07 03:30 – Updated: 2026-10-07 03:30

Details

In wolfSSH through 1.5.0 built with --enable-fwd, DoChannelOpen() in src/internal.c gates only direct-tcpip channel opens with the forwarding policy callback. forwarded-tcpip opens are admitted without an authorization check and are not capped in number, allowing a malicious SSH peer to make an endpoint allocate unbounded per-channel buffers for forwarding channels the application never authorized. A client also does not check a forwarded-tcpip open against the forwards it registered with a tcpip-forward request, as RFC 4254 section 7.2 requires, so a malicious server can open forwarding channels for addresses and ports the client never asked it to forward.

Severity

6.3 (Medium)


                  
                    CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N

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{
  "affected": [],
  "aliases": [
    "CVE-2026-81535"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-862"
    ],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-10-07T03:16:59Z",
    "severity": "MODERATE"
  },
  "details": "In wolfSSH through 1.5.0 built with\u00a0--enable-fwd,\u00a0DoChannelOpen()\u00a0in\u00a0src/internal.c\u00a0gates only\u00a0direct-tcpip\u00a0channel opens with the forwarding policy callback.\u00a0forwarded-tcpip\u00a0opens are admitted without an authorization check and are not capped in number, allowing a malicious SSH peer to make an endpoint allocate unbounded per-channel buffers for forwarding channels the application never authorized. A client also does not check a\u00a0forwarded-tcpip\u00a0open against the forwards it registered with a\u00a0tcpip-forward\u00a0request, as RFC 4254 section 7.2 requires, so a malicious server can open forwarding channels for addresses and ports the client never asked it to forward.",
  "id": "GHSA-cqr9-f685-gr3w",
  "modified": "2026-10-07T03:30:23Z",
  "published": "2026-10-07T03:30:23Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-81535"
    },
    {
      "type": "WEB",
      "url": "https://github.com/wolfSSL/wolfssh/commit/616eb681e70759c30c3ba158f2b18d7bd954def8"
    },
    {
      "type": "WEB",
      "url": "https://github.com/wolfSSL/wolfssh/commit/79a7f299337a28aa561409688a268d0efe6e295c"
    },
    {
      "type": "WEB",
      "url": "https://github.com/wolfSSL/wolfssh/commit/e396a0a4b6b367f10270287446a4be0071742b5c"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X",
      "type": "CVSS_V4"
    }
  ]
}

CVE-2026-81535 (GCVE-0-2026-81535)

Vulnerability from cvelistv5 – Published: 2026-10-07 02:39 – Updated: 2026-10-07 18:37

Title

wolfSSH SSH client accepts unsolicited forwarded-tcpip channel opens without an authorization check

Summary

Severity

6.3 (Medium)


                        
                          CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N

SSVC

Exploitation: none Automatable: no Technical Impact: partial

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-10-07 18:37 UTC

CWE

CWE-862 - Missing Authorization
CWE-863 - Incorrect Authorization

Assigner

wolfSSL CNA under the icscert root

CNA scorecard B 80/100 over 52 records in the last 180 days details

References

3 references

URL	Tags
https://github.com/wolfSSL/wolfssh/commit/616eb68…	patch
https://github.com/wolfSSL/wolfssh/commit/e396a0a…	patch
https://github.com/wolfSSL/wolfssh/commit/79a7f29…	patch

Impacted products

1 product

Vendor	Product	Version
wolfSSL Inc.	wolfSSH	Affected: 1.4.8 , ≤ 1.5.0 (semver)

Credits

zhangph (GitHub afldl)

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JSON

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{
  "containers": {
    "adp": [
      {
        "metrics": [
          {
            "other": {
              "content": {
                "id": "CVE-2026-81535",
                "options": [
                  {
                    "Exploitation": "none"
                  },
                  {
                    "Automatable": "no"
                  },
                  {
                    "Technical Impact": "partial"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-10-07T18:37:10.078645Z",
                "version": "2.0.3"
              },
              "type": "ssvc"
            }
          }
        ],
        "providerMetadata": {
          "dateUpdated": "2026-10-07T18:37:36.186Z",
          "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "shortName": "CISA-ADP"
        },
        "title": "CISA ADP Vulnrichment"
      }
    ],
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "modules": [
            "forwarding"
          ],
          "product": "wolfSSH",
          "programFiles": [
            "src/internal.c"
          ],
          "repo": "https://github.com/wolfSSL/wolfssh",
          "vendor": "wolfSSL Inc.",
          "versions": [
            {
              "changes": [
                {
                  "at": "1.6.0",
                  "status": "unaffected"
                }
              ],
              "lessThanOrEqual": "1.5.0",
              "status": "affected",
              "version": "1.4.8",
              "versionType": "semver"
            }
          ]
        }
      ],
      "credits": [
        {
          "lang": "en",
          "type": "finder",
          "value": "zhangph (GitHub afldl)"
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "supportingMedia": [
            {
              "base64": false,
              "type": "text/html",
              "value": "In wolfSSH through 1.5.0 built with\u0026nbsp;\u003ccode\u003e--enable-fwd\u003c/code\u003e,\u0026nbsp;\u003ccode\u003eDoChannelOpen()\u003c/code\u003e\u0026nbsp;in\u0026nbsp;\u003ccode\u003esrc/internal.c\u003c/code\u003e\u0026nbsp;gates only\u0026nbsp;\u003ccode\u003edirect-tcpip\u003c/code\u003e\u0026nbsp;channel opens with the forwarding policy callback.\u0026nbsp;\u003ccode\u003eforwarded-tcpip\u003c/code\u003e\u0026nbsp;opens are admitted without an authorization check and are not capped in number, allowing a malicious SSH peer to make an endpoint allocate unbounded per-channel buffers for forwarding channels the application never authorized. A client also does not check a\u0026nbsp;\u003ccode\u003eforwarded-tcpip\u003c/code\u003e\u0026nbsp;open against the forwards it registered with a\u0026nbsp;\u003ccode\u003etcpip-forward\u003c/code\u003e\u0026nbsp;request, as RFC 4254 section 7.2 requires, so a malicious server can open forwarding channels for addresses and ports the client never asked it to forward.\u003cbr\u003e"
            }
          ],
          "value": "In wolfSSH through 1.5.0 built with\u00a0--enable-fwd,\u00a0DoChannelOpen()\u00a0in\u00a0src/internal.c\u00a0gates only\u00a0direct-tcpip\u00a0channel opens with the forwarding policy callback.\u00a0forwarded-tcpip\u00a0opens are admitted without an authorization check and are not capped in number, allowing a malicious SSH peer to make an endpoint allocate unbounded per-channel buffers for forwarding channels the application never authorized. A client also does not check a\u00a0forwarded-tcpip\u00a0open against the forwards it registered with a\u00a0tcpip-forward\u00a0request, as RFC 4254 section 7.2 requires, so a malicious server can open forwarding channels for addresses and ports the client never asked it to forward."
        }
      ],
      "impacts": [
        {
          "capecId": "CAPEC-130",
          "descriptions": [
            {
              "lang": "en",
              "value": "CAPEC-130 Excessive Allocation"
            }
          ]
        }
      ],
      "metrics": [
        {
          "cvssV4_0": {
            "Automatable": "NOT_DEFINED",
            "Recovery": "NOT_DEFINED",
            "Safety": "NOT_DEFINED",
            "attackComplexity": "LOW",
            "attackRequirements": "PRESENT",
            "attackVector": "NETWORK",
            "baseScore": 6.3,
            "baseSeverity": "MEDIUM",
            "exploitMaturity": "NOT_DEFINED",
            "privilegesRequired": "NONE",
            "providerUrgency": "NOT_DEFINED",
            "subAvailabilityImpact": "NONE",
            "subConfidentialityImpact": "NONE",
            "subIntegrityImpact": "NONE",
            "userInteraction": "NONE",
            "valueDensity": "NOT_DEFINED",
            "vectorString": "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N",
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            "vulnerabilityResponseEffort": "NOT_DEFINED"
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          "scenarios": [
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          "descriptions": [
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              "description": "CWE-862 Missing Authorization",
              "lang": "en",
              "type": "CWE"
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        },
        {
          "descriptions": [
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              "cweId": "CWE-863",
              "description": "CWE-863 Incorrect Authorization",
              "lang": "en",
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      "providerMetadata": {
        "dateUpdated": "2026-10-07T02:39:27.830Z",
        "orgId": "50d2cd11-d01a-48ed-9441-5bfce9d63b27",
        "shortName": "wolfSSL"
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      "references": [
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          "url": "https://github.com/wolfSSL/wolfssh/commit/616eb681e70759c30c3ba158f2b18d7bd954def8"
        },
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          "name": "Fix commit e396a0a4 (match forwarded-tcpip opens to registered forwards, PR #1148)",
          "tags": [
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          "url": "https://github.com/wolfSSL/wolfssh/commit/e396a0a4b6b367f10270287446a4be0071742b5c"
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          "name": "Fix commit 79a7f299 (match forwarded-tcpip on every client session, PR #1220)",
          "tags": [
            "patch"
          ],
          "url": "https://github.com/wolfSSL/wolfssh/commit/79a7f299337a28aa561409688a268d0efe6e295c"
        }
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      "source": {
        "discovery": "EXTERNAL"
      },
      "title": "wolfSSH SSH client accepts unsolicited forwarded-tcpip channel opens without an authorization check",
      "x_generator": {
        "engine": "Vulnogram 1.0.5"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "50d2cd11-d01a-48ed-9441-5bfce9d63b27",
    "assignerShortName": "wolfSSL",
    "cveId": "CVE-2026-81535",
    "datePublished": "2026-10-07T02:39:27.830Z",
    "dateReserved": "2026-08-26T23:09:37.634Z",
    "dateUpdated": "2026-10-07T18:37:36.186Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}

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.
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GHSA-CQR9-F685-GR3W

CVE-2026-81535 (GCVE-0-2026-81535)

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