CVE-2026-50017: pnpm binds unscoped user-level npm auth credentials to a repository-selected registry

pnpm can send user-level unscoped npm authentication credentials to a registry chosen by a repository-local .npmrc file.

In the reproduced case, the user’s npm config contains a default registry and an unscoped _authToken. The repository does not provide a token-bearing auth line. It only sets registry= to a different registry URL. During normal pnpm metadata/install workflows, pnpm binds the user-origin unscoped credential to the repository-selected registry and sends it as an Authorization header.

This was reproduced with fake credentials and loopback registries only. No third-party registry or real token was used.