CVE-2026-62268: borg extract might modify out-of-tree files when extracting maliciously crafted archives

A maliciously crafted archive could contain a symlink (e.g. “evil” -> “/etc”) followed by an item below it (“evil/passwd”), or an item whose path embeds “..” (e.g. “a/../../etc/passwd”).

When extracting such items, borg followed the symlink / resolved the “..”, so it could delete or overwrite files outside the extraction directory.

In a quite similar scenario, a crafted archive could contain a slave hardlink item with the hardlink source pointing outside the extraction directory.

When extracting such an item, borg would hard-link the outside and the inside item.

Note: that sounds bad, but it is no big issue in practice: to create such a malicious archive, the attacker would need repository access and (for encrypted or authenticated repos) also the borg key and passphrase.

Affected: likely all borg releases before 1.4.5 (and also all borg 2.0.0 betas before b22).