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.
| Product | Vendor Advisory | Solution File | Added | Published |
|---|---|---|---|---|
| Alpine Linux | — | Upgrade cacti | Jun 19, 2026 | Apr 10, 2026 |
| Debian | — | Upgrade php-phpseclib3Upgrade phpseclibUpgrade php-phpseclib | May 17, 2026 | May 17, 2026 |
| Freebsd | — | Upgrade cacti | Jul 9, 2026 | Jul 7, 2026 |
| Ubuntu | — | Upgrade php-phpseclib (Ubuntu Pro) | Sep 29, 2026 | Sep 28, 2026 |
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