CVE-2018-15133

CVE-2018-15133 is a PHP deserialization flaw (CWE-502) in Laravel Framework versions through 5.5.40 and 5.6.x through 5.6.29: the decrypt method in Illuminate/Encryption/Encrypter.php passes the decrypted X-XSRF-TOKEN header value to unserialize, enabling PHP object injection via the PendingBroadcast gadget chain. A remote attacker triggers it by sending a crafted X-XSRF-TOKEN header, but only if they know the application's APP_KEY, which typically happens because the key was leaked (e.g., committed to public GitHub repositories) or reused across deployments. Successful exploitation yields remote code execution on the web server with high impact to confidentiality, integrity, and availability; in current campaigns the AndroxGh0st malware exploits this flaw to steal AWS, Azure, and Office 365 credentials and now also distributes Mozi botnet payloads. Any Laravel 5.5.x or 5.6.x application within the affected ranges is exposed, with practical risk concentrated on apps whose APP_KEY has been exposed or shared. Exploitation is confirmed in the wild: CISA added the flaw to the KEV catalog on 2024-01-16, EPSS puts the 30-day exploitation probability at about 77%, and public scanning has already identified 600+ Laravel apps with leaked APP_KEYs on GitHub.

What to do: Upgrade Laravel Framework to a release later than 5.6.29 (latest patched 5.6.x or a supported major version) per vendor guidance; CISA's KEV required action is to apply vendor mitigations or discontinue use of the product if mitigations are unavailable. Because exploitation requires knowing the APP_KEY, audit and rotate the key, remove it from public repositories and exposed .env files, and hunt for AndroxGh0st activity (suspicious processes, outbound credential theft) on Laravel hosts.