Vulnerability · Published May 26, 2026 · Assigned by GitHub_M
CVE-2026-44903Prometheus: Stored XSS via crafted histogram bucket label values in the heatmap display of the old Prometheus web UI
Medium 5.1
In plain English
A medium-severity cross-site scripting in prometheus from prometheus. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.2% (higher than 10% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official 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.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian:13 | prometheus | no fix listed | DEBIAN-CVE-2026-44903 |
| Debian:14 | prometheus | 3.5.3+ds1-1 | DEBIAN-CVE-2026-44903 |
| Go | github.com/prometheus/prometheus | 0.311.3 | GHSA-fw8g-cg8f-9j28 |
| Go | github.com/prometheus/prometheus | 0.311.3 | GO-2026-5381 |
| Ubuntu:25.10 | prometheus | no fix listed | UBUNTU-CVE-2026-44903 |
| Ubuntu:26.10 | prometheus | no fix listed | UBUNTU-CVE-2026-44903 |
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| prometheus | prometheus | >= 2.49.0, < 3.5.3>= 3.6.0-rc.0, < 3.11.3 |
Weakness: CWE-79 · Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:P/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N