GHSA-v86x-5fm3-5p7j — alertmanager
MEDIUMGHSA-v86x-5fm3-5p7j is a medium-severity (CVSS 5.4) Cross-site Scripting (XSS) vulnerability in github.com/prometheus/alertmanager. A fix is available for github.com/prometheus/alertmanager — see the affected versions and patch details below.
Alertmanager UI is vulnerable to stored XSS via the /api/v1/alerts endpoint
Exploitation Status
No confirmed exploitation observed yet
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for GHSA-v86x-5fm3-5p7j.
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.
How urgent is this, really
GHSA-v86x-5fm3-5p7j plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 377,166 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
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 | 0.25.1go get github.com/prometheus/alertmanager@v0.25.1 |
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, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
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 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like GHSA-v86x-5fm3-5p7j can be triaged on real exposure rather than presence alone.
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.
Fixing This On Your OS
If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.
This vulnerability affects Prometheus Alertmanager v0.25.0, which is not shipped in Red Hat OpenShift container platform, therefore, this is marked as Not affected.
| Product | Fixed in | Advisory |
|---|---|---|
| Red Hat OpenShift Container Platform 4.15 | openshift4/ose-prometheus-alertmanager:v4.15.0-202401290854.p0.g870ade5.assembly.stream | RHSA-2023:7198 |
Frequently Asked Questions
Is GHSA-v86x-5fm3-5p7j in your dependencies?
O3 Security finds GHSA-v86x-5fm3-5p7j across Go dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.