CVE-2026-40176: Composer is vulnerable to Command Injection via Malicious Perforce Repository
Impact The Perforce::generateP4Command() method constructed shell commands by interpolating user-supplied Perforce connection parameters (port, user, client) without proper escaping. An attacker controlling a repository configuration in a malicious composer.json declaring a Perforce VCS repository could inject arbitrary commands through these values, leading to command execution in the context of the user running Composer. Composer would execute these injected commands even if Perforce is not installed.
VCS repositories are only loaded from the root composer.json file located in the directory you execute Composer commands in and from the composer config directory (e.g. ~/.config/composer/composer.json). So this vulnerability cannot be exploited through composer.json files of packages installed as dependencies.
You are at risk of command execution if you run Composer commands on untrusted projects with attacker supplied composer.json files, regardless of whether you or any of your dependencies use Perforce.
Patches Fixed in Composer 2.2.27 (2.2 LTS) and 2.9.6 (mainline)
Workarounds - Carefully inspect composer.json files before running Composer on them. Verify that Perforce-related fields contain valid values. - Only run Composer commands on projects from trusted sources.
Other sources
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).
— MITRE
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
composer/composer/composerto a version that resolves this vulnerability.Fixed in 2.2.27 - Upgrade
Upgrade
composer/composer/composerto a version that resolves this vulnerability.Fixed in 2.9.6 - Upgrade
Upgrade
Composerto a version that resolves this vulnerability.Fixed in 2.2.27 - Upgrade
Upgrade
Composerto a version that resolves this vulnerability.Fixed in 2.9.6 - Configuration
Verify that Perforce-related fields contain valid values before running Composer.
composer.json (Perforce VCS configuration) Perforce-related fields (port/user/client) = valid values only - Compensating control
Only run Composer commands on projects from trusted sources (do not run Composer on untrusted projects with attacker-controlled composer.json).
Event History
Frequently Asked Questions
What is the severity of CVE-2026-40176?
CVE-2026-40176 is considered a critical vulnerability due to improper user input escaping leading to potential code execution.
How does CVE-2026-40176 affect affected software?
CVE-2026-40176 allows attackers to craft malicious commands through the Perforce connection parameters used by affected versions of Composer.
How do I fix CVE-2026-40176?
To fix CVE-2026-40176, upgrade to Composer version 2.2.27 or 2.9.6 to ensure proper input handling.
Which versions of Composer are affected by CVE-2026-40176?
Versions of Composer between 2.0.0 and 2.2.27 and between 2.3.0 and 2.9.6 are affected by CVE-2026-40176.
What kind of attack can CVE-2026-40176 enable?
CVE-2026-40176 can enable remote code execution attacks if a user is tricked into executing a shell command with malicious input.