Description

borgbackup is an opensource, deduplicating archiver with compression and authenticated encryption. A flaw in the cryptographic authentication scheme in borgbackup allowed an attacker to fake archives and potentially indirectly cause backup data loss in the repository. The attack requires an attacker to be able to: 1. insert files (with no additional headers) into backups and 2. gain write access to the repository. This vulnerability does not disclose plaintext to the attacker, nor does it affect the authenticity of existing archives. Creating plausible fake archives may be feasible for empty or small archives, but is unlikely for large archives. The issue has been fixed in borgbackup 1.2.5. Users are advised to upgrade. Additionally to installing the fixed code, users must follow the upgrade procedure as documented in the change log. Data loss after being attacked can be avoided by reviewing the archives (timestamp and contents valid and as expected) after any "borg check --repair" and before "borg prune". There are no known workarounds for this vulnerability.

Severity MEDIUM

CVSS Score 4.7

CVSS Vector CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:H/A:N

CWE CWE-347

Public Exploit ✅ No

Source NVD

Published 2023-08-30

Updated 2026-06-15

Modified 2024-11-21

Fix URL https://github.com/borgbackup/borg/commit/3eb070191da10c2d3f7bc6484cf3d51c3045f884

Software	From version	Fixed in
borg	—	1.2.5
borgbackup	—	1.2.5