GHSA-rvx4-ffvw-m9q3: composer/composer (CVE-2026-84361)

Package	Ecosystem	Affected	Fixed in
composer/composer	Packagist	>=2.3.0, <2.10.3 \|\| >=1.0, <2.2.30	2.10.3, 2.2.30

Machine-written summary

Summary written by Claude Haiku from the source advisory. Not reviewed by a person.

Composer versions from 1.0 before 2.2.30, and from 2.3.0 before 2.10.3, pass a package's Perforce source address to the p4 client without validating it. If the p4 client is installed, an attacker who controls a malicious package in a non-Packagist Composer repository, or a lock file from an untrusted source, could run arbitrary local commands with the privileges of the user or CI account when running composer install or update. Upgrade to Composer 2.10.3 or 2.2.30, which validate Perforce addresses before use; removing the p4 client from machines that do not need it also blocks this attack.

Written 31 Oct 2026.

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

Score	Rating	CVSS	Vector	Source
7.7	High	4.0	CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N	CNA (GitHub_M)

CISA KEV Not listed.
EPSS 0.0050, the 43rd percentile, on 11 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

Timeline

27 Aug 2026, 11:41 UTC Published by the maintainers as a GitHub repository advisory
31 Oct 2026, 14:06 UTC First seen by agentprime
31 Oct 2026, 14:06 UTC Confirmed by OSV

Sources

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.