CVE-2026-40194

LowCVSS 3.7/10Last modified Jun 17, 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.

Metrics

CVSS 3.1 3.7/10CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N

Weakness enumeration

CWE-208

Affected software

Vendor	Product	Versions
phpseclib	phpseclib	>= 0.1.1, < 1.0.28; >= 2.0.0, < 2.0.53; >= 3.0.0, < 3.0.51

References

https://github.com/phpseclib/phpseclib/commit/ffe48b6b1b1af6963327f0a5330e3aa004a194acPatch
https://github.com/phpseclib/phpseclib/releases/tag/1.0.28Release Notes
https://github.com/phpseclib/phpseclib/releases/tag/2.0.53Release Notes
https://github.com/phpseclib/phpseclib/releases/tag/3.0.51Release Notes
https://github.com/phpseclib/phpseclib/security/advisories/GHSA-r854-jrxh-36qxVendor Advisory
https://github.com/phpseclib/phpseclib/security/advisories/GHSA-r854-jrxh-36qxVendor Advisory

Timeline

Published: Apr 10, 2026
Last modified: Jun 17, 2026
NVD status: Modified

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