EUVD-2026-21597
GHSA-r854-jrxh-36qx
CVSS Vector
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N
Lifecycle Timeline
4Description
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.
Analysis
phpseclib's SSH2 packet authentication uses PHP's non-constant-time != operator to compare HMACs, enabling timing-based information disclosure attacks on SSH sessions. The vulnerability affects phpseclib versions prior to 1.0.28, 2.0.53, and 3.0.51. …
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