🛡️ CVE-2026-40194 on Debian — php-phpseclib

⚪ Unknown ✅ No Known Exploit OSV
N/A
CVSS Score
0 Low4 Medium7 High9 Critical10

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.

Distribution advisory

This page covers CVE-2026-40194 as tracked by Debian, for the package php-phpseclib. The fix is available in version 2.0.53-1; earlier versions remain affected.

How this vulnerability can be exploited

This issue can be reached over the network, attack complexity is high, an attacker needs no privileges on the target. No user interaction is required. The scope is unchanged, so the impact stays within the vulnerable component. Rated impact: confidentiality low, integrity none, availability none.

Weakness class

DEBIAN-CVE-2026-40194 is classified as CWE-208: Observable Timing Discrepancy. Two separate operations in a product require different amounts of time to complete, in a way that is observable to an actor and reveals security-relevant information about the state of the product, such as whether a particular operation was successful or not.

Affected software

DEBIAN-CVE-2026-40194 is recorded against 3 packages.

  • php-phpseclib (fixed in 2.0.53-1)
  • php-phpseclib3 (fixed in 3.0.51-1)
  • phpseclib (fixed in 1.0.23-6+deb13u2)

Timeline and source

Published on 10 April 2026 and last revised on 4 August 2026. No public exploit is currently recorded for this entry. Record sourced from OSV.

References

security-tracker.debian.org (Advisory)

CVE-2026-40194 on other distributions

Each distribution ships its own build and its own fixed version. Pick the one you run:

Details

Severity Unknown
CVSS Score N/A
CVSS Vector CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N
CWE N/A
Public Exploit ✅ No
Source OSV
Published 2026-04-10
Updated 2026-08-20
Modified 2026-08-04
Fix URL N/A

Affected Packages

Software From version Fixed in
php-phpseclib — 2.0.53-1
php-phpseclib3 — 3.0.51-1
phpseclib — 1.0.23-6+deb13u2

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