Composer has a command injection via malicious perforce reference

Not analysed yet

We haven’t published our analysis of this Advisory yet. Once a person has reviewed it, this page will say what’s vulnerable, what has to be true for your app to be affected, and how to check.

Severity and exploitation

• CISA KEV Not listed.
• EPSS 0.017, the 77th percentile, on 15 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

Timeline

1. 14 Apr 2026, 09:46 UTC Published by the maintainers as a GitHub repository advisory
2. 31 Oct 2026, 13:59 UTC First seen by agentprime
3. 31 Oct 2026, 13:59 UTC Confirmed by OSV

Sources

• GitHub Advisory Database: GHSA-gqw4-4w2p-838q
• OSV: GHSA-gqw4-4w2p-838q
• github.com/composer/composer/security/advisories/GHSA-gqw4-4w2p-838q
• nvd.nist.gov/vuln/detail/CVE-2026-40261
• access.redhat.com/errata/RHSA-2026:8165
• access.redhat.com/security/cve/CVE-2026-40261
• bugzilla.redhat.com/show_bug.cgi?id=2458841
• github.com/FriendsOfPHP/security-advisories/blob/master/composer/composer/CVE-2026-40261.yaml
• github.com/composer/composer
• github.com/composer/composer/releases/tag/2.9.6
• security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-40261.json

Facts on this page come from the GitHub Advisory Database (CC-BY 4.0), OSV and the other sources listed, as published. We don’t reproduce full advisory descriptions, which can contain exploit code.