FKIE_CVE-2026-81535

Vulnerability from fkie_nvd - Published: 2026-10-07 03:16 - Updated: 2026-10-07 19:17
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
Summary
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.
References
facts@wolfssl.comhttps://github.com/wolfSSL/wolfssh/commit/616eb681e70759c30c3ba158f2b18d7bd954def8
facts@wolfssl.comhttps://github.com/wolfSSL/wolfssh/commit/79a7f299337a28aa561409688a268d0efe6e295c
facts@wolfssl.comhttps://github.com/wolfSSL/wolfssh/commit/e396a0a4b6b367f10270287446a4be0071742b5c
Impacted products
Vendor Product Version
To clipboard 

{
  "affected": [
    {
      "affectedData": [
        {
          "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"
            }
          ]
        }
      ],
      "source": "facts@wolfssl.com"
    }
  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "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."
    }
  ],
  "id": "CVE-2026-81535",
  "lastModified": "2026-10-07T19:17:44.487",
  "metrics": {
    "cvssMetricV40": [
      {
        "cvssData": {
          "Automatable": "NOT_DEFINED",
          "Recovery": "NOT_DEFINED",
          "Safety": "NOT_DEFINED",
          "attackComplexity": "LOW",
          "attackRequirements": "PRESENT",
          "attackVector": "NETWORK",
          "availabilityRequirement": "NOT_DEFINED",
          "baseScore": 6.3,
          "baseSeverity": "MEDIUM",
          "confidentialityRequirement": "NOT_DEFINED",
          "exploitMaturity": "NOT_DEFINED",
          "integrityRequirement": "NOT_DEFINED",
          "modifiedAttackComplexity": "NOT_DEFINED",
          "modifiedAttackRequirements": "NOT_DEFINED",
          "modifiedAttackVector": "NOT_DEFINED",
          "modifiedPrivilegesRequired": "NOT_DEFINED",
          "modifiedSubAvailabilityImpact": "NOT_DEFINED",
          "modifiedSubConfidentialityImpact": "NOT_DEFINED",
          "modifiedSubIntegrityImpact": "NOT_DEFINED",
          "modifiedUserInteraction": "NOT_DEFINED",
          "modifiedVulnAvailabilityImpact": "NOT_DEFINED",
          "modifiedVulnConfidentialityImpact": "NOT_DEFINED",
          "modifiedVulnIntegrityImpact": "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/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",
          "version": "4.0",
          "vulnAvailabilityImpact": "LOW",
          "vulnConfidentialityImpact": "NONE",
          "vulnIntegrityImpact": "NONE",
          "vulnerabilityResponseEffort": "NOT_DEFINED"
        },
        "source": "facts@wolfssl.com",
        "type": "Secondary"
      }
    ],
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "id": "CVE-2026-81535",
          "options": [
            {
              "exploitation": "none"
            },
            {
              "automatable": "no"
            },
            {
              "technicalImpact": "partial"
            }
          ],
          "role": "CISA Coordinator",
          "timestamp": "2026-10-07T18:37:10.078645Z",
          "version": "2.0.3"
        }
      }
    ]
  },
  "published": "2026-10-07T03:16:59.567",
  "references": [
    {
      "source": "facts@wolfssl.com",
      "url": "https://github.com/wolfSSL/wolfssh/commit/616eb681e70759c30c3ba158f2b18d7bd954def8"
    },
    {
      "source": "facts@wolfssl.com",
      "url": "https://github.com/wolfSSL/wolfssh/commit/79a7f299337a28aa561409688a268d0efe6e295c"
    },
    {
      "source": "facts@wolfssl.com",
      "url": "https://github.com/wolfSSL/wolfssh/commit/e396a0a4b6b367f10270287446a4be0071742b5c"
    }
  ],
  "sourceIdentifier": "facts@wolfssl.com",
  "vulnStatus": "Undergoing Analysis",
  "weaknesses": [
    {
      "description": [
        {
          "lang": "en",
          "value": "CWE-862"
        },
        {
          "lang": "en",
          "value": "CWE-863"
        }
      ],
      "source": "facts@wolfssl.com",
      "type": "Secondary"
    }
  ]
}



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