CVE-2026-40194

LOW3.7EPSS 0.01%

phpseclib has a variable-time HMAC comparison in SSH2::get_binary_packet() using != instead of hash_equals()

Published: 4/10/2026Modified: 5/27/2026

Description

phpseclib is a PHP secure communications library. Starting in 0.1.1 and 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.

Affected packages (4)

CVSS scores

SourceVersionSeverityVector
osvCVSS 3.1LOW3.7CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N

References (8)