Prometheus: Stored XSS in Web UI via Metric Names and Label Values

This CVE does not affect KrakenD

KrakenD uses the Prometheus client library (prometheus/client_golang) to expose a /metrics scrape endpoint and does not embed or serve the Prometheus web UI. The vulnerable JavaScript rendering components are part of the Prometheus server application, which KrakenD does not include. The dependency was upgraded as a precaution.

Addressed through routine dependency maintenance in CE 2.13.5 and EE 2.13.3.

Component

Prometheus client library

Disclosed

May 11, 2026

CVSS Score

6.1

Description

Multiple components of the Prometheus web UI inject metric names and label values into innerHTML without HTML escaping. An attacker with the ability to write metrics — via remote write, OTLP, or compromised scrape targets — can inject arbitrary JavaScript that executes in users’ browsers when they view the Prometheus web UI.

References

View CVE-2026-40179 on NVD

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