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Vulnerability record · CVE-2026-40194 · published 10 April 2026

CVE-2026-40194: Phpseclib vulnerability

Phpseclib · Phpseclib

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.

3.7 CVSS 3.1 Low EPSS 0.37% · top 72.0% CWE-208 · CWE-208
3.7CVSS 3.1 base score
0.37%EPSS exploitation probability, 30 days
NoNot in CISA KEV
1Affected product versions listed by NVD
6References
17 Jun 2026Last modified by NVD

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.

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

Affected products

1 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://github.com/phpseclib/phpseclib/commit/ffe48b6b1b1af6963327f0a5330e3aa004a194ac Patch
https://github.com/phpseclib/phpseclib/releases/tag/1.0.28 Release Notes
https://github.com/phpseclib/phpseclib/releases/tag/2.0.53 Release Notes
https://github.com/phpseclib/phpseclib/releases/tag/3.0.51 Release Notes
https://github.com/phpseclib/phpseclib/security/advisories/GHSA-r854-jrxh-36qx Vendor Advisory
https://github.com/phpseclib/phpseclib/security/advisories/GHSA-r854-jrxh-36qx Vendor Advisory

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Related vulnerabilities

Same products first, then exploited flaws of the same weakness class.

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Source: NIST National Vulnerability Database (record CVE-2026-40194), CISA KEV, FIRST EPSS (scores of 2026-09-27). This page is refreshed as NVD updates the record.