GHSA-v86x-5fm3-5p7j
MEDIUMAlertmanager UI is vulnerable to stored XSS via the /api/v1/alerts endpoint
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
github.com/prometheus/alertmanagerReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects Go packages — download data is not available via public APIs for these ecosystems.
Description
Impact
An attacker with the permission to perform POST requests on the /api/v1/alerts endpoint could be able to execute arbitrary JavaScript code on the users of Prometheus Alertmanager.
Patches
Users can upgrade to Alertmanager v0.2.51.
Workarounds
Users can setup a reverse proxy in front of the Alertmanager web server to forbid access to the /api/v1/alerts endpoint.
References
N/A
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐹Go | github.com/prometheus/alertmanager | all versions | 0.25.1 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/prometheus/alertmanager. 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 github.com/prometheus/alertmanager to 0.25.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-v86x-5fm3-5p7j 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-v86x-5fm3-5p7j 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-v86x-5fm3-5p7j. 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-v86x-5fm3-5p7j in your dependencies?
O3 detects GHSA-v86x-5fm3-5p7j across Go dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.