CVE-2026-40176

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.

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.

The application does not adequately validate input before processing it, allowing unexpected values to reach sensitive code paths. Typical impact: varies by context: data corruption, logic bypass, or denial of service.

CVE-2026-40176 has a CVSS score of 7.8 (High). The vector is requires local access, no privileges required, and user interaction required. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (2.9.6, 2.2.27); upgrading removes the vulnerable code path.

Kodem intelligence

Fixed in Composer 2.2.27 (2.2 LTS) and 2.9.6 (mainline)

1. What is CVE-2026-40176? CVE-2026-40176 is a high-severity improper input validation vulnerability in composer/composer (composer), affecting versions >= 2.3.0, < 2.9.6. It is fixed in 2.9.6, 2.2.27. The application does not adequately validate input before processing it, allowing unexpected values to reach sensitive code paths.
2. How severe is CVE-2026-40176? CVE-2026-40176 has a CVSS score of 7.8 (High). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which versions of composer/composer are affected by CVE-2026-40176? composer/composer (composer) versions >= 2.3.0, < 2.9.6 is affected.
4. Is there a fix for CVE-2026-40176? Yes. CVE-2026-40176 is fixed in 2.9.6, 2.2.27. Upgrade to this version or later.
5. Is CVE-2026-40176 exploitable, and should I be worried? Whether CVE-2026-40176 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2026-40176 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2026-40176?
   • Upgrade composer/composer to 2.9.6 or later
   • Upgrade composer/composer to 2.2.27 or later