Vulnerability in Phpseclib
CVE-2026-40194
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.
EPSS: 0.004 (28.8th percentile) — read the EPSS interpretation.
CVSS v3 metric
CVSS v3 base score 3.7 (Low). Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N.
Affected products
- Phpseclib — versions >= 3.0.0, < 3.0.51, >= 2.0.0, < 2.0.53, >= 0.1.1, < 1.0.28
Weakness classification (CWE)
References
- security-advisories@github.com (x_refsource_CONFIRM, Vendor Advisory)
- security-advisories@github.com (Patch, x_refsource_MISC)
- security-advisories@github.com (x_refsource_MISC, Release Notes)
- security-advisories@github.com (x_refsource_MISC, Release Notes)
- security-advisories@github.com (x_refsource_MISC, Release Notes)
Frequently asked questions
- What is CVE-2026-40194?
- CVE-2026-40194 is a low-severity vulnerability in Phpseclib, classified under CWE-208. CVSS score: 3.7/10. Published 2026-04-10.
- How severe is CVE-2026-40194?
- Low severity. CVSS v3 base score is 3.7 out of 10.