CVE-2026-59946
MEDIUMComposer: Path traversal in package bin field lets dependencies chmod arbitrary host files
Blast Radius
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 a dependency Manager for the PHP language. Prior to 2.2.29 and 2.10.2, a Composer package bin entry containing .. path segments can resolve outside the package install directory and cause Composer's binary installation flow to chmod an existing host file to a world-readable and world-executable mode during composer install, update, or require. This issue is fixed in versions 2.2.29 and 2.10.2.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐘Packagist | composer/composer | ≥ 2.3.0&&< 2.10.2 | 2.10.2 |
| 🐘Packagist | composer/composer | ≥ 1.0.0&&< 2.2.29 | 2.2.29 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for composer/composer. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update composer/composer to 2.10.2 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-59946 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether CVE-2026-59946 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to CVE-2026-59946. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2026-59946 in your dependencies?
O3 detects CVE-2026-59946 across Packagist dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.