Composer is vulnerable to Command Injection via Malicious Perforce Repository

Description

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).

Scores

EPSS (exploitation in 30 days)

1.0% · top 36% of all CVEs (5 Nov 2026)

CISA SSVC

Exploitation: none · Automatable: no · Technical impact: total

The list uses the assigner's score when there is one, then CISA's, then NVD's: High 7.8.

Weakness

• CWE-20: Improper Input Validation (opens in a new tab)All about CWE-20 and its CVEs
• CWE-78: Improper Neutralization of Special Elements used in an OS Command ('OS Command Injection') (opens in a new tab)All about CWE-78 and its CVEs

Affected products

• composer · composer

  • affected >= 2.3, < 2.9.6
  • affected >= 1.0, < 2.2.27

Affected packages

From reviewed advisories of the GitHub Advisory Database.

• Packagistcomposer/composerGHSA-wg36-wvj6-r67p (opens in a new tab)

References (8)

• https://github.com/composer/composer/security/advisories/GHSA-wg36-wvj6-r67p (opens in a new tab)x_refsource_CONFIRM
• https://access.redhat.com/errata/RHSA-2026:8165 (opens in a new tab)x_refsource_MISCvendor-advisoryx_refsource_REDHAT
• https://access.redhat.com/security/cve/CVE-2026-40176 (opens in a new tab)x_refsource_MISCvdb-entryx_refsource_REDHAT
• https://bugzilla.redhat.com/show_bug.cgi?id=2458828 (opens in a new tab)x_refsource_MISCissue-trackingx_refsource_REDHAT
• https://github.com/FriendsOfPHP/security-advisories/blob/master/composer/composer/CVE-2026-40176.yaml (opens in a new tab)x_refsource_MISC
• https://github.com/composer/composer/releases/tag/2.2.27 (opens in a new tab)x_refsource_MISC
• https://github.com/composer/composer/releases/tag/2.9.6 (opens in a new tab)x_refsource_MISC
• https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-40176.json (opens in a new tab)x_refsource_MISCx_sadp-csaf-vex

Sources

The same CVE in the primary databases and aggregators, to check against.

• CVE.org record (opens in a new tab)
• CVE List JSON (GitHub) (opens in a new tab)
• NVD (opens in a new tab)
• FIRST EPSS (opens in a new tab)
• OSV.dev (opens in a new tab)
• GitHub Advisory GHSA-wg36-wvj6-r67p (opens in a new tab)
• CIRCL Vulnerability-Lookup (opens in a new tab)

Badge for a README or a ticket

[![CVE-2026-40176](https://trackcve.app/badge/CVE-2026-40176.svg)](https://trackcve.app/cve/CVE-2026-40176)

Record last updated 2 Nov 2026, 23:04 UTC.