CVE-2026-50015: pnpm Vulnerable to Arbitrary File Write/Delete via Malicious Patch File (Path Traversal)

pnpm’s patch application pipeline (@pnpm/patch-package) performs no path validation on file paths extracted from .patch files. An attacker who contributes a malicious patch file via a pull request can write attacker-controlled content to or delete arbitrary files on the filesystem during pnpm install, as the user running the install. The diff --git header paths containing ../../ sequences traverse out of the package directory, and the traversal is difficult to catch in code review because patch file diff headers are opaque to most reviewers.