Bug 2535546 (CVE-2026-59944)

Summary: CVE-2026-59944 composer: Composer: Security bypass allows execution of unauthorized binaries via symlinked paths
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
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Priority: medium    
Version: unspecifiedKeywords: Security
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OS: Linux   
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A flaw was found in Composer, a dependency manager for PHP. A malicious or compromised dependency can bypass existing security measures designed to prevent unauthorized binary path execution. This can occur when Composer processes untrusted cached data or older build artifacts, allowing it to follow symlinked paths outside of its intended installation directory. As a result, Composer may change the permissions of external files to make them executable and create proxy entries, potentially leading to the execution of unauthorized binaries.
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Description OSIDB Bzimport 2026-09-16 16:25:55 UTC 
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.