Composer up to 2.2.26/2.9.5 generateP4Command input validation

Summaryinfo

A vulnerability described as problematic has been identified in Composer up to 2.2.26/2.9.5. Impacted is the function Perforce::generateP4Command. Such manipulation leads to input validation. This vulnerability is traded as CVE-2026-40176. An attack has to be approached locally. There is no exploit available. Upgrading the affected component is recommended.

Detailsinfo

A vulnerability, which was classified as problematic, has been found in Composer up to 2.2.26/2.9.5. Affected by this issue is the function Perforce::generateP4Command. The manipulation with an unknown input leads to a input validation vulnerability. Using CWE to declare the problem leads to CWE-20. The product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly. Impacted is confidentiality, integrity, and availability. CVE summarizes:

Composer is a dependency manager for PHP. Versions 1.0 through 2.2.26 and 2.3 through 2.9.5 contain a command injection vulnerability in the Perforce::generateP4Command() method, which constructs shell commands by interpolating user-supplied Perforce connection parameters (port, user, client) without proper escaping. An attacker can inject arbitrary commands through these values in a malicious composer.json declaring a Perforce VCS repository, leading to command execution in the context of the user running Composer, even if Perforce is not installed. VCS repositories are only loaded from the root composer.json or the composer config directory, so this cannot be exploited through composer.json files of packages installed as dependencies. Users are at risk if they run Composer commands on untrusted projects with attacker-supplied composer.json files. This issue has been fixed in Composer 2.2.27 (2.2 LTS) and 2.9.6 (mainline).

The advisory is shared for download at github.com. This vulnerability is handled as CVE-2026-40176 since 04/09/2026. The exploitation is known to be easy. The attack needs to be approached locally. There are known technical details, but no exploit is available.

The vulnerability scanner Nessus provides a plugin with the ID 306621 (Fedora 43 : composer (2026-02c1f66b6a)), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 2.2.27 or 2.9.6 eliminates this vulnerability. The upgrade is hosted for download at github.com.

The vulnerability is also documented in the vulnerability database at Tenable (306621). VulDB is the best source for vulnerability data and more expert information about this specific topic.

Productinfo

Name

• Composer

Version

• 2.2.0
• 2.2.1
• 2.2.2
• 2.2.3
• 2.2.4
• 2.2.5
• 2.2.6
• 2.2.7
• 2.2.8
• 2.2.9
• 2.2.10
• 2.2.11
• 2.2.12
• 2.2.13
• 2.2.14
• 2.2.15
• 2.2.16
• 2.2.17
• 2.2.18
• 2.2.19
• 2.2.20
• 2.2.21
• 2.2.22
• 2.2.23
• 2.2.24
• 2.2.25
• 2.2.26
• 2.9.0
• 2.9.1
• 2.9.2
• 2.9.3
• 2.9.4
• 2.9.5

Website

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

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CPE 2.2info

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VulDB is the best source for vulnerability data and more expert information about this specific topic.

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