CVE-2026-44903

MEDIUM

Prometheus: Stored XSS via crafted histogram bucket label values in the heatmap display of the old Prometheus web UI

Title source: cna
STIX 2.1

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.

References (2)

Core 2

Scores

CVSS v3 6.1
EPSS 0.0015
EPSS Percentile 4.1%
Attack Vector NETWORK
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

CISA SSVC

Vulnrichment
Exploitation none
Automatable no
Technical Impact partial

Details

CWE
CWE-79
Status published
Products (4)
prometheus/prometheus 0 - 0.311.3Go
prometheus/prometheus 2.49.0 - 3.5.3
prometheus/prometheus >= 2.49.0, < 3.5.3
prometheus/prometheus >= 3.6.0-rc.0, < 3.11.3
Published May 26, 2026
Tracked Since May 27, 2026