pnpm: `patch-remove` could delete project-selected files outside the patches directory

Summary

The patch-remove deletion-scope issue tracked as GHSA-72r4-9c5j-mj57 / CAND-PNPM-030 has been addressed in pnpm.

A crafted patch entry could resolve outside the configured patches directory and cause pnpm patch-remove to delete an arbitrary reachable file. This patch validates the configured directory and every resolved target before unlinking anything, then deletes the final directory entry without following it.

Security boundary

• Traversal and absolute paths that resolve outside the configured patches directory are rejected before deletion.
• Parent directories are canonicalized before deletion, including the case where a nested symlink points outside and the final outside entry is itself dangling.
• The complete batch is validated before any file is removed.
• Component-aware predicates accept valid names beginning with .. while still rejecting parent traversal, Windows drive escapes, and UNC escapes.
• Valid files and symlinked patch directories whose canonical targets remain below the lockfile directory continue to work.
• A final symlink inside a valid patch directory is unlinked without following its target, including when the target is outside or dangling.

Exploit replay

Before the patch, a workspace patchedDependencies path that resolved outside the project caused pnpm patch-remove to delete the external sentinel. A second replay used a nested parent symlink and a dangling outside victim: realpath() returned ENOENT, yet the victim was still removed. With this patch, both paths are rejected and the outside entries remain intact.

Files changed

• patching/commands/src/isSubdirectory.ts performs component-aware containment checks.
• patching/commands/src/patchRemove.ts validates the full batch, canonicalizes parents, and unlinks final entries without following them.
• patching/commands/test/{isSubdirectory,patchRemove}.test.ts covers traversal, nested symlinks, dangling victims, and valid removals.

Commands run

$ pnpm --filter @pnpm/patching.commands test test/isSubdirectory.test.ts test/patchRemove.test.ts
PASS: 11 tests across 2 suites
$ pnpm --filter @pnpm/patching.commands run compile
PASS
$ git diff --check
PASS

Validation

• Focused handler and path-predicate suites: 11 passed across 2 suites.
• Package-wide ESLint: passed.
• Package TypeScript build: passed.