VulnerabilityAnalyzed

CVE-2026-44903

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.

MEDIUM 5.1EPSS 0.20%

Does this matter?

Lower severity and a low EPSS score (0.20%). Track it; it rarely justifies an emergency change on its own.

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.

CVSS 4.0: 5.1 MEDIUMCVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:P/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/M
EPSS: 0.20% probability · 11th percentile
CISA KEV: Not listed
Weakness: CWE-79
Affected: prometheus/prometheus
Source: security-advisories@github.com

References

https://github.com/prometheus/prometheus/commit/38f23b9075ced1de2b82d2dad8b2bebb1ecd5b7dPatch
https://github.com/prometheus/prometheus/security/advisories/GHSA-fw8g-cg8f-9j28Mitigation, Patch, Vendor Advisory

Source: NVD record, EPSS from FIRST.org, KEV from CISA. Refreshed daily.