{"id":"CVE-2026-81535","aliases":["ALPINE-CVE-2026-81535","EUVD-2026-94162","GHSA-cqr9-f685-gr3w"],"status":"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.","severity":{"version":"4.0","score":6.3,"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","level":"medium","assessor":"cna","from":"cve"},"epss":{"day":"2026-11-10","score":0.00305,"percentile":0.23499,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":true},"cwes":["CWE-862","CWE-863"],"published":"2026-10-07T02:39:27Z","modified":"2026-11-03T06:33:06Z","fixes":[{"ecosystem":"Alpine:v3.24","package":"wolfssh","fixed_in":["1.6.0-r0"],"sources":["osv"]}],"affected":[{"source":"osv","ecosystem":"Alpine:v3.24","package":"wolfssh","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1.6.0-r0"}]}]}],"products":[{"vendor":"wolfssh","product":"wolfssh"},{"vendor":"wolfssl","product":"wolfssh"},{"vendor":"wolfssl inc.","product":"wolfssh"}],"references":[{"url":"https://github.com/wolfSSL/wolfssh/commit/616eb681e70759c30c3ba158f2b18d7bd954def8","tags":["patch","Patch","fix"]},{"url":"https://github.com/wolfSSL/wolfssh/commit/e396a0a4b6b367f10270287446a4be0071742b5c","tags":["patch","Patch","fix"]},{"url":"https://github.com/wolfSSL/wolfssh/commit/79a7f299337a28aa561409688a268d0efe6e295c","tags":["patch","Patch","fix"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-81535","tags":["advisory"]},{"url":"https://github.com/advisories/GHSA-cqr9-f685-gr3w"},{"url":"https://security.alpinelinux.org/vuln/CVE-2026-81535","tags":["advisory"]},{"url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/81xxx/CVE-2026-81535.json","tags":["advisory"]},{"url":"https://github.com/wolfSSL/wolfssh","tags":["package"]}],"sources":{"cve":[{"id":"CVE-2026-81535","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.","status":"published","published":"2026-10-07T02:39:27.83Z","modified":"2026-10-07T18:37:36.186Z","cvss":[{"version":"4.0","score":6.3,"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","level":"medium","assessor":"cna"}],"cwes":["CWE-862","CWE-863"],"updated_at":"2026-11-02T13:36:29.327819Z"}],"euvd":[{"id":"EUVD-2026-94162","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.","status":"published","published":"2026-10-07T02:39:27Z","modified":"2026-10-07T18:37:36Z","cvss":[{"version":"4.0","score":6.3,"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","level":"medium"}],"updated_at":"2026-11-02T17:27:34.353796Z"}],"ghsa":[{"id":"GHSA-cqr9-f685-gr3w","title":"In wolfSSH through 1.5.0 built with --enable-fwd, DoChannelOpen() in src/internal.c gates only...","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.","status":"published","published":"2026-10-07T03:30:23Z","modified":"2026-10-13T18:31:30Z","cvss":[{"version":"4.0","score":6.3,"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/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","level":"medium"},{"version":"3.1","score":9.1,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N","level":"critical"}],"cwes":["CWE-862"],"updated_at":"2026-11-02T15:13:12.080152Z"}],"nvd":[{"id":"CVE-2026-81535","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.","status":"published","published":"2026-10-07T03:16:59.567Z","modified":"2026-10-13T17:36:15.9Z","cvss":[{"version":"4.0","score":6.3,"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/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","level":"medium","assessor":"secondary"},{"version":"3.1","score":9.1,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N","level":"critical","assessor":"primary"}],"cwes":["CWE-862","CWE-863"],"updated_at":"2026-11-02T14:12:54.809359Z"}],"osv":[{"id":"ALPINE-CVE-2026-81535","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.","status":"published","published":"2026-10-07T03:16:59.567Z","modified":"2026-11-03T06:33:06.495888115Z","cvss":[{"version":"3.1","score":9.1,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N","level":"critical"}],"updated_at":"2026-11-03T07:15:37.282377Z"},{"id":"CVE-2026-81535","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.","status":"published","published":"2026-10-07T02:39:27.83Z","modified":"2026-10-28T11:12:27.725753697Z","cvss":[{"version":"4.0","score":6.3,"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","level":"medium"}],"cwes":["CWE-862","CWE-863"],"updated_at":"2026-11-02T15:45:18.131258Z"}]}}