pdm is a Python package and dependency manager supporting the latest PEP standards. It's possible to craft a malicious `pdm.lock` file that could allow e.g. an insider or a malicious open source project to appear to depend on a trusted PyPI project, but actually install another project. A project `foo` can be targeted by creating the project `foo-2` and uploading the file `foo-2-2.tar.gz` to pypi.org. PyPI will see this as project `foo-2` version `2`, while PDM will see this as project `foo` version `2-2`. The version must only be `parseable as a version` and the filename must be a prefix of the project name, but it's not verified to match the version being installed. Version `2-2` is also not a valid normalized version per PEP 440. Matching the project name exactly (not just prefix) would fix the issue. When installing dependencies with PDM, what's actually installed could differ from what's listed in `pyproject.toml` (including arbitrary code execution on install). It could also be used for downgrade attacks by only changing the version. This issue has been addressed in commit `6853e2642df` which is included in release version `2.9.4`. Users are advised to upgrade. There are no known workarounds for this vulnerability.

https://github.com/pdm-project/pdm/commit/6853e2642dfa281d4a9958fbc6c95b7e32d84831
https://github.com/frostming/unearth/blob/eca170d9370ac5032f2e497ee9b1b63823d3fe0f/src/unearth/evaluator.py#L215-L229
https://github.com/pdm-project/pdm/security/advisories/GHSA-j44v-mmf2-xvm9
https://github.com/pdm-project/pdm/blob/45d1dfa47d4900c14a31b9bb761e4c46eb5c9442/src/pdm/models/candidates.py#L98-L99
https://peps.python.org/pep-0440/#post-release-spelling