CVE-2026-40194

LOW

phpseclib SSH2::get_binary_packet() - Variable-Time HMAC Comparison

Title source: manual
STIX 2.1

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.

References (5)

Core 5

Scores

CVSS v3 3.7
EPSS 0.0033
EPSS Percentile 25.0%
Attack Vector NETWORK
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N

CISA SSVC

Vulnrichment
Exploitation poc
Automatable no
Technical Impact partial

Details

CWE
CWE-208
Status published
Products (8)
phpseclib/phpseclib < 1.0.27
phpseclib/phpseclib 0.1.1 - 1.0.28Packagist
phpseclib/phpseclib 2.0.0 - 2.0.53Packagist
phpseclib/phpseclib 3.0.0 - 3.0.51Packagist
phpseclib/phpseclib < 1.0.28
phpseclib/phpseclib >= 0.1.1, < 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