How severe is GHSA-vffh-x6r8-xx99?

GHSA-vffh-x6r8-xx99 has a CVSS score of 6.1/10, rated MEDIUM. Review your exposure and patch according to your risk tolerance.

Which packages are affected by GHSA-vffh-x6r8-xx99?

GHSA-vffh-x6r8-xx99 affects the following packages: github.com/prometheus/prometheus (Go), github.com/prometheus/prometheus (Go), github.com/prometheus/prometheus (Go). Ecosystems affected: Go.

How do I fix GHSA-vffh-x6r8-xx99?

Update github.com/prometheus/prometheus to 3.5.2 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-vffh-x6r8-xx99 is resolved across your whole dependency graph.

How do I detect GHSA-vffh-x6r8-xx99 in my Go dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/prometheus/prometheus, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate GHSA-vffh-x6r8-xx99 if there is no patch (or I can't update yet)?

Escape or sanitise the affected output on the server side rather than relying on client-side filtering, and add a Content-Security-Policy that blocks inline script execution so injected markup cannot run even if it reaches the page.

Is GHSA-vffh-x6r8-xx99 actively exploited in the wild?

No public exploit code has been indexed for GHSA-vffh-x6r8-xx99 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for GHSA-vffh-x6r8-xx99?

GHSA-vffh-x6r8-xx99 has an EPSS (Exploit Prediction Scoring System) score of 0.3%, placing it in the 24th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is GHSA-vffh-x6r8-xx99?

GHSA-vffh-x6r8-xx99 is classified as Cross-site Scripting (XSS) (CWE-79). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation. This is a high-impact weakness class that often enables remote code execution or data exposure.

When was GHSA-vffh-x6r8-xx99 published, and has it been updated?

GHSA-vffh-x6r8-xx99 was published on April 13, 2026 and was last updated on October 6, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

🐹

🐹 Go

Not in CISA KEV

MEDIUM severity

Prometheus has Stored XSS via metric names and label values in Prometheus web UI tooltips and metrics explorerGHSA-vffh-x6r8-xx99

MEDIUMFix: prometheus/prometheus#18506

GHSA-vffh-x6r8-xx99 is a medium-severity (CVSS 6.1) Cross-site Scripting (XSS) vulnerability in github.com/prometheus/prometheus. A fix is available for github.com/prometheus/prometheus — see the affected versions and patch details below.

Also known asBIT-prometheus-2026-40179CVE-2026-40179GO-2026-5662

Published

Apr 13, 2026

Updated

Oct 6, 2026

Affected

3 pkgs

Patched

3 / 3

Exploits

None indexed

Exploitation data as of Nov 10, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

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-vffh-x6r8-xx99.

EPSS Exploitation Probability

via FIRST.org ↗

0.3%probability of exploitation in next 30 days

Lower Risk+0.05%

Lower risk than most CVEs24th percentile — riskier than 24% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

Where this sits among everything scored

Real-World Exposure

3 pkgs affected

🐹github.com/prometheus/prometheus🐹github.com/prometheus/prometheus🐹github.com/prometheus/prometheus

Real-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

Stored cross-site scripting (XSS) via crafted metric names in the Prometheus web UI:

Old React UI + New Mantine UI: When a user hovers over a chart tooltip on the Graph page, metric names containing HTML/JavaScript are injected into innerHTML without escaping, causing arbitrary script execution in the user's browser.
Old React UI only: When a user opens the Metric Explorer (globe icon next to the PromQL expression input field), and a metric name containing HTML/JavaScript is rendered in the fuzzy search results, it is injected into innerHTML without escaping, causing arbitrary script execution in the user's browser.
Old React UI only: When a user views a heatmap chart and hovers over a cell, the le label values of the underlying histogram buckets are interpolated into innerHTML without escaping. While le is conventionally a numeric bucket boundary, Prometheus does not enforce this — arbitrary UTF-8 strings are accepted as label values, allowing script injection via a crafted scrape target or remote write.

With Prometheus v3.x defaulting to UTF-8 metric and label name validation, characters like <, >, and " are now valid in metric names and labels, making this exploitable.

An attacker who can inject metrics (via a compromised scrape target, remote write, or OTLP receiver endpoint) can execute JavaScript in the browser of any Prometheus user who views the metric in the Graph UI. From the XSS context, an attacker could for example:

Read /api/v1/status/config to extract sensitive configuration (although credentials / secrets are redacted by the server)
Call /-/quit to shut down Prometheus (only if --web.enable-lifecycle is set)
Call /api/v1/admin/tsdb/delete_series to delete data (only if --web.enable-admin-api is set)
Exfiltrate metric data to an external server

Both the new Mantine UI and the old React UI are affected. The vulnerable code paths are:

web/ui/mantine-ui/src/pages/query/uPlotChartHelpers.ts — tooltip innerHTML with unescaped labels.__name__
web/ui/react-app/src/pages/graph/GraphHelpers.ts — tooltip content with unescaped labels.__name__
web/ui/react-app/src/pages/graph/MetricsExplorer.tsx — fuzzy search results rendered via dangerouslySetInnerHTML without sanitization
web/ui/react-app/src/vendor/flot/jquery.flot.heatmap.js — heatmap tooltip with unescaped label values

Patches

A patch has been published in Prometheus 3.5.2 LTS and Prometheus 3.11.2. The fix applies escapeHTML() to all user-controlled values (metric names and label values) before inserting them into innerHTML. This advisory will be updated with the patched version once released.

Workarounds

If using the remote write receiver (--web.enable-remote-write-receiver), ensure it is not exposed to untrusted sources.
If using the OTLP receiver (--web.enable-otlp-receiver), ensure it is not exposed to untrusted sources.
Ensure scrape targets are trusted and not under attacker control.
Do not enable admin / mutating API endpoints (e.g. --web.enable-admin-api or web.enable-lifecycle) in cases where you cannot prevent untrusted data from being ingested.
Users should avoid clicking untrusted links, especially those containing functions such as label_replace, as they may generate poisoned label names and values.

References

CVE-2019-10215 — prior stored DOM XSS vulnerability in Prometheus query history, fixed in v2.7.2

Acknowledgements

Thanks to @gladiator9797 (Duc Anh Nguyen from TinyxLab) for reporting this.

Affected Packages

3 total 3 fixed

Ecosystem	Package	Vulnerable range	Fix
🐹Go	`github.com/prometheus/prometheus`	≥ 3.0.0&&< 3.5.2	3.5.2`go get github.com/prometheus/prometheus@v3.5.2`
🐹Go	`github.com/prometheus/prometheus`	≥ 3.6.0&&< 3.11.2	3.11.2`go get github.com/prometheus/prometheus@v3.11.2`
🐹Go	`github.com/prometheus/prometheus`	all versions	0.311.2-0.20260410083055-07c6232d159b`go get github.com/prometheus/prometheus@v0.311.2-0.20260410083055-07c6232d159b`

Affected Products

1 product · 2 configurations

Application

prometheusprometheus

≥ 3.6.0 && < 3.11.2

range

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/prometheus/prometheus, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update github.com/prometheus/prometheus to 3.5.2 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-vffh-x6r8-xx99 is resolved across your whole dependency graph.
Workarounds
Escape or sanitise the affected output on the server side rather than relying on client-side filtering, and add a Content-Security-Policy that blocks inline script execution so injected markup cannot run even if it reaches the page.

Frequently Asked Questions

### Impact Stored cross-site scripting (XSS) via crafted metric names in the Prometheus web UI: * **Old React UI + New Mantine UI:** When a user hovers over a chart tooltip on the Graph page, metric names containing HTML/JavaScript are injected into `innerHTML` without escaping, causing arbitrary script execution in the user's browser. * **Old React UI only:** When a user opens the Metric Explorer (globe icon next to the PromQL expression input field), and a metric name containing HTML/JavaScript is rendered in the fuzzy search results, it is injected into `innerHTML` without escaping, causi