BorgBackup CVE-2026-62268

Exploitation requires the attacker to have write access to the borg repository in order to inject a maliciously crafted archive, because 'borg create' never emits a child below a symlinked parent or a path containing '..' - the malicious items must be written directly into the repository, bypassing normal archive creation. For encrypted or authenticated repositories, the attacker additionally needs the borg encryption key and passphrase. The victim must then actively run 'borg extract' on the malicious archive for the symlink-following, '..'-resolution, or out-of-tree hardlinking to occur. These preconditions (privileged repository access plus key/passphrase, plus required victim action) are the primary limiting factors and sharply reduce realistic risk; no special non-default borg configuration is otherwise needed, and default extraction behavior in vulnerable versions is affected.

This is a genuine but low-urgency flaw whose real-world risk is heavily gated by prerequisites. No CVSS, EPSS, KEV, SSVC, or POC data is present in the input, so quantitative exploitation signals are entirely absent - this means the assessment rests on the description and CWE-59 (link following) rather than any scoring framework. The vulnerability (symlinked-parent following, '..' path traversal, and out-of-tree hardlinking during 'borg extract') can overwrite or delete files outside the extraction directory, including sensitive targets like /etc/passwd. Critically, however, the vendor advisory itself states exploitation requires repository access and, for encrypted or authenticated repositories, the borg encryption key and passphrase to craft the malicious archive - a very high bar that places this closer to an attacker-already-has-privileged-access scenario than a remotely weaponizable issue. There is no evidence of active exploitation and no public exploit; the issue was found proactively by an AI-assisted code review and independently reported by two researchers, not observed in attacks. Net: a legitimate integrity/availability bug worth patching, but not a drop-everything emergency absent the strong preconditions.

An attacker who already holds write access to a borg repository (and the key/passphrase for encrypted repos) injects a crafted archive containing a symlink such as 'evil' -> '/etc' followed by 'evil/passwd', or an item with an embedded '..' path. When a victim later runs 'borg extract' on that archive, borg follows the symlink or resolves the '..' and overwrites or deletes files outside the intended extraction directory. No public exploit code is known; the proof of concept exists only as a vendor regression test that injects raw Item objects directly into a repository.