CVE-2026-81535: medium-severity vulnerability in wolfSSL Inc. wolfSSH
wolfSSH SSH client accepts unsolicited forwarded-tcpip channel opens without an authorization check
Published
13Vexday Risk Score
No sign of exploitation. No public exploitation artifact known so far.
ssvc Trackcvss 6.3epss 0.3%
exploitation probability
0.3%top 82% of all CVEs
observed exploitation
nono source reports it
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.
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
Affected products
wolfSSL Inc. · wolfSSHRelated CVEs — wolfSSL Inc. wolfSSH
In the same product, most dangerous first.
CVE-2024-2873CRITICALUser authentication bypass in wolfSSH serverEPSS 0.6%CVE-2026-83742MEDIUMwstrncat() unsigned integer underflow leads to an off-by-one null write in wolfSSH on non-Windows platformsEPSS 0.3%CVE-2026-84897MEDIUMwolfSSH server accepts server-to-client DH group exchange messages from an unauthenticated client, causing pre-authentication primality-test CPU exhaustion and key exchange role confusionEPSS 0.3%CVE-2026-16516CRITICALwolfSSH ECDSA host key curve not validated against negotiated algorithmEPSS 0.1%