CVE-2026-44903
Medium
Description
Prometheus is an open-source monitoring system and time series database. From 2.49.0 to before 3.5.3 and 3.11.3, in the Prometheus server's legacy web UI (enabled via the command-line flag --enable-feature=old-ui), the histogram heatmap chart view does not escape le label values when inserting them into the HTML for use as axis tick mark labels. An attacker who can inject crafted metrics can execute JavaScript in the browser of any Prometheus user who views the metric in the heatmap chart UI. This vulnerability is fixed in 3.5.3 and 3.11.3.
SeverityMedium
CVSS6.1
Exploit probability—
Product
Prometheus
PublishedMay 26, 2026
First seenMay 26, 2026
Weakness typeCWE-79Cross-site scripting (XSS)
How to fix
Update
- prometheus prometheus3.5.3, 3.11.3 or later
- github.com/prometheus/prometheus0.311.3 or later
Affected products
| Product | Affected versions | Fixed in |
|---|---|---|
| prometheus prometheus | 2.49.0 ≤ v < 3.5.3, 3.6.0 ≤ v < 3.11.3 | 3.5.3, 3.11.3 |
| github.com/prometheus/prometheusGo | v < 0.311.3 | 0.311.3 |
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