AIKIDO-2026-727366

TL;DR

Composer does not fully validate the names of packages produced by dependency resolution before writing them to composer.lock or installing them. A maliciously crafted package served from an untrusted third-party repository can use an invalid package name to make Composer write attacker-controlled files outside the vendor/ directory and outside the project during a normal install or update. This arbitrary file write can be leveraged to execute code outside the expected package context by planting shell startup files, SSH authorized_keys, or cron entries. The fix validates every resolved package name and aborts with a security error when a name is not a valid vendor/package name.