phpseclib up to 1.0.27/2.0.52/3.0.50 SSH2::get_binary_packet timing discrepancy

Summaryinfo

A vulnerability, which was classified as problematic, has been found in phpseclib up to 1.0.27/2.0.52/3.0.50. The affected element is the function SSH2::get_binary_packet. The manipulation leads to timing discrepancy. This vulnerability is referenced as CVE-2026-40194. Remote exploitation of the attack is possible. No exploit is available. It is advisable to upgrade the affected component.

Detailsinfo

A vulnerability was found in phpseclib up to 1.0.27/2.0.52/3.0.50 and classified as problematic. This issue affects the function SSH2::get_binary_packet. The manipulation with an unknown input leads to a timing discrepancy vulnerability. Using CWE to declare the problem leads to CWE-208. 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. Impacted is confidentiality. The summary by CVE is:

phpseclib is a PHP secure communications library. 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.

The advisory is shared at github.com. The identification of this vulnerability is CVE-2026-40194 since 04/09/2026. The exploitation is known to be difficult. The attack may be initiated remotely. No form of authentication is needed for a successful exploitation. Technical details are known, but no exploit is available. MITRE ATT&CK project uses the attack technique T1592 for this issue.

The vulnerability scanner Nessus provides a plugin with the ID 306030 (Linux Distros Unpatched Vulnerability : CVE-2026-40194), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 1.0.28, 2.0.53 or 3.0.51 eliminates this vulnerability. The upgrade is hosted for download at github.com. Applying the patch ffe48b6b1b1af6963327f0a5330e3aa004a194ac is able to eliminate this problem. The bugfix is ready for download at github.com. The best possible mitigation is suggested to be upgrading to the latest version.

The vulnerability is also documented in the vulnerability database at Tenable (306030). Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

Productinfo

Name

• phpseclib

Version

• 1.0.0
• 1.0.1
• 1.0.2
• 1.0.3
• 1.0.4
• 1.0.5
• 1.0.6
• 1.0.7
• 1.0.8
• 1.0.9
• 1.0.10
• 1.0.11
• 1.0.12
• 1.0.13
• 1.0.14
• 1.0.15
• 1.0.16
• 1.0.17
• 1.0.18
• 1.0.19
• 1.0.20
• 1.0.21
• 1.0.22
• 1.0.23
• 1.0.24
• 1.0.25
• 1.0.26
• 1.0.27
• 2.0.0
• 2.0.1
• 2.0.2
• 2.0.3
• 2.0.4
• 2.0.5
• 2.0.6
• 2.0.7
• 2.0.8
• 2.0.9
• 2.0.10
• 2.0.11
• 2.0.12
• 2.0.13
• 2.0.14
• 2.0.15
• 2.0.16
• 2.0.17
• 2.0.18
• 2.0.19
• 2.0.20
• 2.0.21
• 2.0.22
• 2.0.23
• 2.0.24
• 2.0.25
• 2.0.26
• 2.0.27
• 2.0.28
• 2.0.29
• 2.0.30
• 2.0.31
• 2.0.32
• 2.0.33
• 2.0.34
• 2.0.35
• 2.0.36
• 2.0.37
• 2.0.38
• 2.0.39
• 2.0.40
• 2.0.41
• 2.0.42
• 2.0.43
• 2.0.44
• 2.0.45
• 2.0.46
• 2.0.47
• 2.0.48
• 2.0.49
• 2.0.50
• 2.0.51
• 2.0.52
• 3.0.0
• 3.0.1
• 3.0.2
• 3.0.3
• 3.0.4
• 3.0.5
• 3.0.6
• 3.0.7
• 3.0.8
• 3.0.9
• 3.0.10
• 3.0.11
• 3.0.12
• 3.0.13
• 3.0.14
• 3.0.15
• 3.0.16
• 3.0.17
• 3.0.18
• 3.0.19
• 3.0.20
• 3.0.21
• 3.0.22
• 3.0.23
• 3.0.24
• 3.0.25
• 3.0.26
• 3.0.27
• 3.0.28
• 3.0.29
• 3.0.30
• 3.0.31
• 3.0.32
• 3.0.33
• 3.0.34
• 3.0.35
• 3.0.36
• 3.0.37
• 3.0.38
• 3.0.39
• 3.0.40
• 3.0.41
• 3.0.42
• 3.0.43
• 3.0.44
• 3.0.45
• 3.0.46
• 3.0.47
• 3.0.48
• 3.0.49
• 3.0.50

License

• open-source

Website

• Product: https://github.com/phpseclib/phpseclib/

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Sourcesinfo

Entryinfo

Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

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