CVE-2026-59944: Composer: CVE-2026-59946 fix bypass via symlinked package bin path
Composer is a dependency Manager for the PHP language. From 1.0 until 2.2.30 and from 2.3.0 until 2.10.3, a malicious or compromised dependency can bypass the earlier CVE-2026-59946 binary-path hardening because Composer validates literal parent-directory segments only during dependency resolution, while the symlink and installed-metadata paths described by the advisory skip that validation. A package can ship an in-package binary symlink that resolves outside its installation directory, or attacker-influenced vendor/composer/installed.json metadata can provide an escaping binary path during a reinstall or regeneration of missing vendor/bin entries. The installed-metadata path is reachable only when the vendor directory was not populated by the same validated install run, such as when it is restored from an untrusted cache, copied from an earlier build stage, carried over from an older Composer run, or writable by a lower-trust build step. Composer can follow the path, change the external target's permissions to make it world-readable and executable, and create a runnable vendor/bin proxy to that external file. The issue does not directly read or transmit data and does not by itself provide remote code execution. This issue is fixed in versions 2.2.30 and 2.10.3.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
Composerto a version that resolves this vulnerability.Fixed in 2.2.30 - Upgrade
Upgrade
Composerto a version that resolves this vulnerability.Fixed in 2.10.3
Event History
Frequently Asked Questions
Which Composer installations are in scope?
The affected ranges are Composer 1.0 through 2.2.30 and Composer 2.3.0 through 2.10.3. Exposure depends on processing a malicious or compromised dependency, or on using attacker-influenced installed metadata under the described conditions.
What does an attacker need to control to use either attack path?
A dependency can include a binary symlink that resolves outside its installation directory. Alternatively, an attacker needs influence over vendor/composer/installed.json and a reinstall or regeneration of missing vendor/bin entries when the vendor directory was not populated by the same validated install run.
Which build and cache practices make the installed-metadata path relevant?
This path is reachable when vendor is restored from an untrusted cache, copied from an earlier build stage, retained from an older Composer run, or writable by a lower-trust build step. A vendor directory produced by the same validated install run does not meet that stated prerequisite.
What is the resulting impact on files outside the package directory?
Composer can follow the escaping path, make the external target world-readable and executable, and create a runnable vendor/bin proxy to it. The issue does not itself directly read or transmit data.