CVE-2021-41116 is a critical-severity (CVSS 9.8) CWE-77 vulnerability in composer/composer. A fix is available for composer/composer — see the affected versions and patch details below.
Improper escaping of command arguments on Windows leading to command injection
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
CVE-2021-41116 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.
Where this sits among everything scored
Of 385,738 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.
Real-World Exposure
composer/composer🐘composer/composerReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects Packagist packages — download data is not available via public APIs for these ecosystems.
Description
Composer is an open source dependency manager for the PHP language. In affected versions windows users running Composer to install untrusted dependencies are subject to command injection and should upgrade their composer version. Other OSs and WSL are not affected. The issue has been resolved in composer versions 1.10.23 and 2.1.9. There are no workarounds for this issue.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐘Packagist | composer/composer | all versions | 1.10.23composer require composer/composer:^1.10.23 |
| 🐘Packagist | composer/composer | ≥ 2.0.0-alpha1&&< 2.1.9 | 2.1.9composer require composer/composer:^2.1.9 |
Affected Products
composergetcomposertenable.sctenableDetection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for composer/composer, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update composer/composer to 1.10.23 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-41116 is resolved across your whole dependency graph.
Workarounds
Stop passing untrusted input into the interpreter or shell: call the affected binary with an argument array rather than a composed command string, reject anything outside a strict allowlist of expected values, and run the component under an account that cannot reach beyond the work it legitimately does.
Frequently Asked Questions
Is CVE-2021-41116 in your dependencies?
Find it across Packagist, including transitive dependencies.