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.

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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
Fixes

Solution

No solution given by the vendor.


Workaround

No workaround given by the vendor.

History

Wed, 27 May 2026 16:30:00 +0000

Type Values Removed Values Added
Metrics ssvc

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


Tue, 26 May 2026 22:45:00 +0000

Type Values Removed Values Added
First Time appeared Prometheus
Prometheus prometheus
Vendors & Products Prometheus
Prometheus prometheus

Tue, 26 May 2026 21:45:00 +0000

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'}


Projects

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cve-icon MITRE

Status: PUBLISHED

Assigner: GitHub_M

Published:

Updated: 2026-05-27T14:20:35.919Z

Reserved: 2026-05-07T21:50:33.547Z

Link: CVE-2026-44903

cve-icon Vulnrichment

Updated: 2026-05-27T14:20:32.176Z

cve-icon NVD

Status : Awaiting Analysis

Published: 2026-05-26T22:16:43.010

Modified: 2026-05-29T16:19:35.753

Link: CVE-2026-44903

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-05-26T23:00:17Z

Weaknesses