{"id":"CVE-2026-81535","state":"PUBLISHED","title":"wolfSSH SSH client accepts unsolicited forwarded-tcpip channel opens without an authorization check","description":"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.","publishedAt":"2026-10-07T02:39:27.830Z","updatedAt":"2026-10-07T18:37:36.186Z","severity":{"score":6.3,"label":"Medium","version":"4.0","vector":"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","source":"wolfSSL"},"assigner":"wolfSSL","products":["wolfSSL Inc. wolfSSH"],"affected":[{"vendor":"wolfSSL Inc.","product":"wolfSSH","defaultStatus":"unaffected","versions":[{"version":"1.4.8","status":"affected","lessThanOrEqual":"1.5.0","changes":[{"at":"1.6.0","status":"unaffected"}],"versionType":"semver"}],"repo":"https://github.com/wolfSSL/wolfssh","modules":["forwarding"],"programFiles":["src/internal.c"]}],"references":["https://github.com/wolfSSL/wolfssh/commit/616eb681e70759c30c3ba158f2b18d7bd954def8","https://github.com/wolfSSL/wolfssh/commit/e396a0a4b6b367f10270287446a4be0071742b5c","https://github.com/wolfSSL/wolfssh/commit/79a7f299337a28aa561409688a268d0efe6e295c"],"weaknesses":["CWE-862","CWE-863"],"ingestedAt":"2026-10-29T20:13:15.269Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/81xxx/CVE-2026-81535.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-81535","state":"PUBLISHED","datePublished":"2026-10-07T02:39:27.830Z","dateUpdated":"2026-10-07T18:37:36.186Z","assignerShortName":"wolfSSL","assignerOrgId":"50d2cd11-d01a-48ed-9441-5bfce9d63b27","dateReserved":"2026-08-26T23:09:37.634Z"},"containers":{"cna":{"title":"wolfSSH SSH client accepts unsolicited forwarded-tcpip channel opens without an authorization check","descriptions":[{"lang":"en","value":"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."}],"affected":[{"vendor":"wolfSSL Inc.","product":"wolfSSH","defaultStatus":"unaffected","versions":[{"version":"1.4.8","status":"affected","lessThanOrEqual":"1.5.0","changes":[{"at":"1.6.0","status":"unaffected"}],"versionType":"semver"}],"repo":"https://github.com/wolfSSL/wolfssh","modules":["forwarding"],"programFiles":["src/internal.c"]}],"references":[{"url":"https://github.com/wolfSSL/wolfssh/commit/616eb681e70759c30c3ba158f2b18d7bd954def8","tags":["patch"]},{"url":"https://github.com/wolfSSL/wolfssh/commit/e396a0a4b6b367f10270287446a4be0071742b5c","name":"Fix commit e396a0a4 (match forwarded-tcpip opens to registered forwards, PR #1148)","tags":["patch"]},{"url":"https://github.com/wolfSSL/wolfssh/commit/79a7f299337a28aa561409688a268d0efe6e295c","name":"Fix commit 79a7f299 (match forwarded-tcpip on every client session, PR #1220)","tags":["patch"]}],"metrics":[{"format":"CVSS","scenarios":[{"lang":"en","value":"GENERAL"}],"cvssV4_0":{"attackVector":"NETWORK","attackComplexity":"LOW","attackRequirements":"PRESENT","privilegesRequired":"NONE","userInteraction":"NONE","vulnConfidentialityImpact":"NONE","subConfidentialityImpact":"NONE","vulnIntegrityImpact":"NONE","subIntegrityImpact":"NONE","vulnAvailabilityImpact":"LOW","subAvailabilityImpact":"NONE","exploitMaturity":"NOT_DEFINED","Safety":"NOT_DEFINED","Automatable":"NOT_DEFINED","Recovery":"NOT_DEFINED","valueDensity":"NOT_DEFINED","vulnerabilityResponseEffort":"NOT_DEFINED","providerUrgency":"NOT_DEFINED","version":"4.0","baseSeverity":"MEDIUM","baseScore":6.3,"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"}}],"problemTypes":[{"descriptions":[{"cweId":"CWE-862","lang":"en","description":"CWE-862 Missing Authorization","type":"CWE"}]},{"descriptions":[{"cweId":"CWE-863","lang":"en","description":"CWE-863 Incorrect Authorization","type":"CWE"}]}],"providerMetadata":{"shortName":"wolfSSL","orgId":"50d2cd11-d01a-48ed-9441-5bfce9d63b27","dateUpdated":"2026-10-07T02:39:27.830Z"},"impacts":[{"capecId":"CAPEC-130","descriptions":[{"lang":"en","value":"CAPEC-130 Excessive Allocation"}]}],"credits":[{"lang":"en","value":"zhangph (GitHub afldl)","type":"finder"}],"source":{"discovery":"EXTERNAL"},"x_generator":{"engine":"Vulnogram 1.0.5"}},"adp":[{"title":"CISA ADP Vulnrichment","metrics":[{"other":{"type":"ssvc","content":{"timestamp":"2026-10-07T18:37:10.078645Z","id":"CVE-2026-81535","options":[{"Exploitation":"none"},{"Automatable":"no"},{"Technical Impact":"partial"}],"role":"CISA Coordinator","version":"2.0.3"}}}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-10-07T18:37:36.186Z"}}]}}}