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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.

PUBLISHED Reserved 2026-04-09 | Published 2026-04-10 | Updated 2026-05-08 | Assigner GitHub_M




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

Problem types

CWE-208: Observable Timing Discrepancy

Product status

>= 0.1.1, < 1.0.28
affected

>= 2.0.0, < 2.0.53
affected

>= 3.0.0, < 3.0.51
affected

References

github.com/...seclib/security/advisories/GHSA-r854-jrxh-36qx exploit

github.com/...seclib/security/advisories/GHSA-r854-jrxh-36qx

github.com/...ommit/ffe48b6b1b1af6963327f0a5330e3aa004a194ac

github.com/phpseclib/phpseclib/releases/tag/1.0.28

github.com/phpseclib/phpseclib/releases/tag/2.0.53

github.com/phpseclib/phpseclib/releases/tag/3.0.51

cve.org (CVE-2026-40194)

nvd.nist.gov (CVE-2026-40194)

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