CVE-2026-40194
phpseclib has a variable-time HMAC comparison in SSH2::get_binary_packet() using != instead of hash_equals()
CVSS Score
3.7
EPSS Score
0.0%
EPSS Percentile
1th
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.
| CWE | CWE-208 |
| Vendor | phpseclib |
| Product | phpseclib |
| Published | Apr 10, 2026 |
| Last Updated | Apr 13, 2026 |
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CVSS v3 Breakdown
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N Attack Vector
Network
Attack Complexity
High
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
Low
Integrity
None
Availability
None
Affected Versions
phpseclib / phpseclib
< 1.0.28 >= 2.0.0, < 2.0.53 >= 3.0.0, < 3.0.51
References
github.com: https://github.com/phpseclib/phpseclib/security/advisories/GHSA-r854-jrxh-36qx github.com: https://github.com/phpseclib/phpseclib/commit/ffe48b6b1b1af6963327f0a5330e3aa004a194ac github.com: https://github.com/phpseclib/phpseclib/releases/tag/1.0.28 github.com: https://github.com/phpseclib/phpseclib/releases/tag/2.0.53 github.com: https://github.com/phpseclib/phpseclib/releases/tag/3.0.51