Arbitrary file permission modification during extraction via vulnerable `tar` dependency (CVE-2026-33056) <br />

[dywzju09-blip]

Error Description:
We discovered that PyOxidizer relies on an outdated tar crate (0.4.43) which is vulnerable to CVE-2026-33056. This vulnerability exists in tar versions < 0.4.45. When PyOxidizer extracts a Python distribution archive (e.g., via python_distribution_extract()), a maliciously crafted .tar.zst file can bypass intended extraction directory boundaries and arbitrarily modify the permissions of external directories on the host filesystem.
Reproduction Steps:

1. Create an external target directory on the host system with restricted permissions: mkdir /tmp/victim && chmod 700 /tmp/victim.
2. Craft a malicious .tar.zst archive (evil.tar.zst) that contains a directory entry pointing to ../../../../tmp/victim with 0777 permissions in its header.
3. Run PyOxidizer (or a script calling python_distribution_extract()) to extract evil.tar.zst into a local destination folder.
4. Check the permissions of the external /tmp/victim directory: stat -c "%a" /tmp/victim.

Observable Evidence / Impact:
The extraction succeeds without throwing any path-traversal or permission errors. However, the permissions of the external /tmp/victim directory are silently escalated.

project=PyOxidizer
archive=evil.tar.zst
mode_before=700
extract_ok=true
mode_after=777

Suggested Mitigation:
Please update the tar dependency in Cargo.toml to >= 0.4.45.