CVE-2026-40194

Name: CVE-2026-40194
Creator: NVD / NIST
Published: 2026-04-10T21:16:27.583+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

LOWCVSS 3.7/10EPSS 0.33%

Last modified Jun 17, 2026

CVE-2026-40194 is a low-severity vulnerability rated 3.7/10 on the CVSS scale. 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. EPSS estimates a 0.33% chance of exploitation in the next 30 days.

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.

Metrics

CVSS 3.1

3.7/10

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

EPSS Probability

0.33%

25.2th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-208

Affected Software

Vendor	Product	Versions
Phpseclib	Phpseclib	<= 1.0.27
Phpseclib	Phpseclib	>= 2.0.0, < 2.0.53
Phpseclib	Phpseclib	>= 3.0.0, < 3.0.51

References

https://github.com/phpseclib/phpseclib/commit/ffe48b6b1b1af6963327f0a5330e3aa004a194acPatch
https://github.com/phpseclib/phpseclib/releases/tag/1.0.28Release Notes
https://github.com/phpseclib/phpseclib/releases/tag/2.0.53Release Notes
https://github.com/phpseclib/phpseclib/releases/tag/3.0.51Release Notes
https://github.com/phpseclib/phpseclib/security/advisories/GHSA-r854-jrxh-36qxVendor Advisory
https://github.com/phpseclib/phpseclib/security/advisories/GHSA-r854-jrxh-36qxVendor Advisory

Timeline

Published: Apr 10, 2026
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2026-40194?

How severe is CVE-2026-40194?

CVE-2026-40194 has a CVSS score of 3.7/10 (LOW severity). The EPSS model estimates a 0.33% probability of exploitation in the next 30 days.

How do I fix CVE-2026-40194?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2026-40194?

Run a free Strix scan to check your systems for this vulnerability.

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Source: NVD / NIST