CVE-2026-40194: Phpseclib

Low severity, CVSS 3.7. EPSS: 0.4% chance of exploitation in the next 30 days.

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 products

• Phpseclib Phpseclib: up to and including 1.0.27; from 2.0.0, before 2.0.53 (fixed in 2.0.53); from 3.0.0, before 3.0.51 (fixed in 3.0.51)

Published 2026-04-10. Last modified 2026-06-17.