Turbo: Unexpected local code execution during Yarn Berry detection

Impact

Turborepo can be vulnerable to arbitrary code execution when run in untrusted repositories that contain malicious Yarn configuration. In affected versions, package manager detection executed yarn --version from the project directory, which could cause Yarn to load and execute a project-controlled yarnPath from .yarnrc.yml. An attacker who controls repository contents could cause code execution when a user or CI system runs affected turbo, @turbo/codemod, or @turbo/workspace conversion commands.

Fix

Turbo now avoids executing project-local Yarn during package manager detection. Yarn versions and paths are inferred from metadata such as package.json, parsing the value of yarnPath in .yarnrc.yml rather than executing it, and yarn.lock, and unrecognized Yarn lockfile formats are rejected instead of falling back to executing yarn.

Workarounds

If you cannot upgrade immediately, do not run Turborepo commands in untrusted repositories. Review or remove .yarnrc.yml files that define yarnPath before running Turborepo, especially in CI or automated tooling that processes external projects.