CVE-2026-40194

LOW

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

Title source: cna

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.

References (5)

Scores

CVSS v3 3.7
EPSS 0.0001
EPSS Percentile 2.3%
Attack Vector NETWORK
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N

Details

CWE
CWE-208
Status published
Products (5)
phpseclib/phpseclib < 1.0.27
phpseclib/phpseclib 0 - 1.0.28Packagist
phpseclib/phpseclib < 1.0.28
phpseclib/phpseclib >= 2.0.0, < 2.0.53
phpseclib/phpseclib >= 3.0.0, < 3.0.51
Published Apr 10, 2026
Tracked Since Apr 11, 2026