CVE-2026-44903

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

Published May 26, 2026 CVSS 4.0 · 5.1 Medium EPSS < 1% KEV · Not listed
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.

Remediation

No solution or workaround provided in the CVE record

Tracking

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Advisories

Source ID Title
Github GHSA Github GHSA GHSA-fw8g-cg8f-9j28 Prometheus vulnerable to stored XSS via crafted histogram bucket label values in the old web UI heatmap display
History
Type Values Removed Values Added
CPEs cpe:2.3:a:prometheus:prometheus:*:*:*:*:*:*:*:*
Metrics cvssV3_1

{'score': 6.1, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N'}

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Type Values Removed Values Added
First Time appeared Prometheus
Prometheus prometheus
Vendors & Products Prometheus
Prometheus prometheus
Type Values Removed Values Added
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.
Title Prometheus: Stored XSS via crafted histogram bucket label values in the heatmap display of the old Prometheus web UI
Weaknesses CWE-79
References
Metrics cvssV4_0

{'score': 5.1, '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'}

Weaknesses

Sources

Status
PUBLISHED
Assigner
GitHub_M
Published
Updated
May 27, 2026, 2:20 PM
Reserved
May 7, 2026, 9:50 PM
Status
Analyzed
Published
May 26, 2026, 10:16 PM
Modified
Jul 24, 2026, 12:10 PM