Is CVE-2026-40194 exploited in the wild?

No. Junglewise Threat Intelligence has no report of CVE-2026-40194 being exploited in the wild.

How severe is CVE-2026-40194?

Low severity, with a CVSS score of 3.7, published 10 April 2026.

Which products and versions are affected?

phpseclib/phpseclib (Packagist) ECOSYSTEM:introduced=0.1.1,fixed=1.0.28.

Is there a fix for CVE-2026-40194?

Yes. phpseclib/phpseclib (Packagist): upgrade to 1.0.28 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

How is CVE-2026-40194 attacked?

It is attacked over the network, in a software library.

Am I affected by CVE-2026-40194?

Check whether you run phpseclib/phpseclib (Packagist) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

CVE-2026-40194: phpseclib timing discrepancy in SSH2 HMAC verification

CVE-2026-40194 · Severity: low · CVSS 3.7 · Published 2026-04-10

phpseclib is a widely used PHP library for secure communications, such as connecting to servers via SSH. A flaw was found where the library compares security codes (HMACs) in a way that takes slightly different amounts of time depending on how much of the code is correct. While difficult to exploit over a network, a sophisticated attacker could theoretically use these timing differences to eventually guess valid security codes, potentially compromising the integrity of the encrypted connection.

Technologies: phpseclib/phpseclib (Packagist). Vendors: Packagist.

Quick answers

Is CVE-2026-40194 exploited in the wild?: No. Junglewise Threat Intelligence has no report of CVE-2026-40194 being exploited in the wild.
How severe is CVE-2026-40194?: Low severity, with a CVSS score of 3.7, published 10 April 2026.
Which products and versions are affected?: phpseclib/phpseclib (Packagist) ECOSYSTEM:introduced=0.1.1,fixed=1.0.28.
Is there a fix for CVE-2026-40194?: Yes. phpseclib/phpseclib (Packagist): upgrade to 1.0.28 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-40194 attacked?: It is attacked over the network, in a software library.
Am I affected by CVE-2026-40194?: Check whether you run phpseclib/phpseclib (Packagist) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

How to fix

phpseclib/phpseclib (Packagist): upgrade to 1.0.28 or later
```
composer require phpseclib/phpseclib:^1.0.28
```

Technical details

The phpseclib library's SSH2 implementation in `get_binary_packet()` uses PHP's `!=` operator to compare received SSH packet HMACs against locally computed HMACs. Because PHP's `!=` operator on equal-length binary strings utilizes `memcmp()`, it short-circuits upon encountering the first differing byte, creating an observable timing discrepancy (CWE-208). An attacker could potentially exploit this side-channel to conduct a timing attack, although practical exploitation is significantly hindered by SSH's default behavior of disconnecting upon MAC failure and the use of per-session keys. The vulnerability affects all non-AEAD ciphers (e.g., AES-CBC, AES-CTR) and is resolved by replacing the inequality operator with the constant-time `hash_equals()` function.

Affected products

phpseclib phpseclib 0.1.1 to 1.0.27, 2.0.0 to 2.0.52, 3.0.0 to 3.0.50

Identifiers

CVE-2026-40194
GHSA-r854-jrxh-36qx

Timeline

2026-04-10: advisory: Vendor advisory and GHSA published
2026-04-10: patched: Fixed in versions 3.0.51, 2.0.53, and 1.0.28

References

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