How severe is CVE-2026-40179?

No CVSS score has been assigned to CVE-2026-40179 yet. Review the advisory details and affected package list to assess your exposure.

Which packages are affected by CVE-2026-40179?

CVE-2026-40179 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 CVE-2026-40179?

No patched version of github.com/prometheus/prometheus has shipped for CVE-2026-40179 yet. Where your build allows, override or pin the dependency away from the vulnerable range, and apply any maintainer-recommended mitigation.

How do I detect CVE-2026-40179 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 CVE-2026-40179 if there is no patch (or I can't update yet)?

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 does O3 Security protect against CVE-2026-40179?

O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2026-40179 can be triaged on real exposure rather than presence alone.

Is CVE-2026-40179 actively exploited in the wild?

No public exploit code has been indexed for CVE-2026-40179 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 CVE-2026-40179?

CVE-2026-40179 has an EPSS (Exploit Prediction Scoring System) score of 0.3%, placing it in the 22th 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 CVE-2026-40179?

CVE-2026-40179 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 CVE-2026-40179 published, and has it been updated?

CVE-2026-40179 was published on April 15, 2026 and was last updated on August 12, 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

CVE-2026-40179 — prometheus

Fix: prometheus/prometheus@07c6232

CVE-2026-40179 is a 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.

Prometheus: Stored XSS via metric names and label values in web UI tooltips and metrics explorer

Also known asBIT-prometheus-2026-40179GHSA-vffh-x6r8-xx99GO-2026-5662

Published

Apr 15, 2026

Updated

Aug 12, 2026

Affected

3 pkgs

Patched

1 / 3

Exploits

None indexed

Exploitation data as of Sep 24, 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 CVE-2026-40179.

EPSS Exploitation Probability

via FIRST.org ↗

0.3%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs22th percentile — riskier than 22% of all scored CVEsHighest risk

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.

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.

Acknowledgements

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

Affected Packages

3 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
🐹Go	`github.com/prometheus/prometheus`	≥ 3.0.0	No fix
🐹Go	`github.com/prometheus/prometheus`	≥ 3.6.0	No fix
🐹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`

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
No patched version of github.com/prometheus/prometheus has shipped for CVE-2026-40179 yet. Where your build allows, override or pin the dependency away from the vulnerable range, and apply any maintainer-recommended mitigation.
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 CVE-2026-40179 can be triaged on real exposure rather than presence alone.

Tailored to CVE-2026-40179. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.

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

O3 Security · Impact-Aware SCA

Is CVE-2026-40179 in your dependencies?

O3 Security finds CVE-2026-40179 across Go dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.

Scan my dependencies How O3 SCA works

CVE-2026-40179 — prometheus

Exploitation Status

No confirmed exploitation observed yet

EPSS Exploitation Probability

Real-World Exposure

Description

Impact

Patches

Workarounds

Acknowledgements

Affected Packages

Detection & mitigation playbook

Detect

Fix

Workarounds

How O3 protects you

Frequently Asked Questions

Is CVE-2026-40179 in your dependencies?