Unsafe reflection in composer - #VU165353
Published: November 11, 2026
Vulnerability identifier: #VU165353
CSH Severity: High
CVSS v4: 8.4 [CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:A/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N]
CVE-ID: N/A
CWE-ID: CWE-470
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a remote attacker to execute arbitrary system commands.
The vulnerability exists due to unsafe loading of externally controlled callbacks in Composer's transport-options.prevent_url_access_callable handling when resolving downloads during composer install or composer update. A remote attacker can craft composer.lock or vendor/composer/installed.json and induce execution of either operation to run arbitrary commands before integrity checks, without installing a malicious package or executing package code.
Affected software
composer
Remediation
Install security update from vendor's website.
composer - update to 2.11.2