CVE-2026-40194

Description

phpseclib is a PHP secure communications library. Prior to 3.0.51, 2.0.53, and 1.0.28, phpseclib\Net\SSH2::get_binary_packet() uses PHP's != operator to compare a received SSH packet HMAC against the locally computed HMAC. != on equal-length binary strings in PHP uses memcmp(), which short-circuits on the first differing byte. This is a real variable-time comparison (CWE-208), proven by scaling benchmarks. This vulnerability is fixed in 3.0.51, 2.0.53, and 1.0.28.

CVSS Vector

References

• https://github.com/phpseclib/phpseclib/commit/ffe48b6b1b1af6963327f0a5330e3aa004a194ac
• https://github.com/phpseclib/phpseclib/releases/tag/1.0.28
• https://github.com/phpseclib/phpseclib/releases/tag/2.0.53
• https://github.com/phpseclib/phpseclib/releases/tag/3.0.51
• https://github.com/phpseclib/phpseclib/security/advisories/GHSA-r854-jrxh-36qx