GHSA-8fjr-hghr-4m99
MEDIUMArchive spoofing vulnerability in borgbackup
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
Blast Radius
borgbackupReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects PyPI packages — download data is not available via public APIs for these ecosystems.
Description
Impact
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
- insert files (with no additional headers) into backups
- 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.
Affected are all borgbackup releases prior to 1.2.5.
Note: CVSS scoring model seemed to badly fit for this case, thus I manually set score to "moderate".
Patches
The issue has been fixed in borgbackup 1.2.5. But there was a bug in 1.2.5 upgrade instructions, thus 1.2.6 with an important fix in docs and code was released a day afterwards.
Additionally to installing the fixed code, users must follow the upgrade procedure as documented in the latest version of the change log.
Workarounds
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".
References
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐍PyPI | borgbackup | all versions | 1.2.5 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for borgbackup. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update borgbackup to 1.2.5 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-8fjr-hghr-4m99 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether GHSA-8fjr-hghr-4m99 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to GHSA-8fjr-hghr-4m99. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is GHSA-8fjr-hghr-4m99 in your dependencies?
O3 detects GHSA-8fjr-hghr-4m99 across PyPI dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.