CPython tarfile filters allow escape via hard link to symlink

CPython's tarfile module has a high-severity flaw in its data and tar extraction filters that can let a malicious archive reach outside the intended destination.

In versions 3.13 and earlier, an archive that pairs a hard link with a symbolic link can cause extraction to change permissions or modification times on a file outside the target directory, or to surface that file's contents inside the extracted tree. The issue is tracked as CVE-2026-82049.

Anyone who extracts untrusted tar archives with the filtered extraction paths is affected. The vulnerability does not require the older, unrestricted extract behavior; it hits the filters meant to make extraction safer. Python's security team published the advisory, pointing maintainers and users to the CVE record for fixed releases and further detail.

Operators who unpack third-party or user-supplied tarballs should treat this as a prompt to upgrade once patches are available, and to avoid extracting untrusted archives until then.