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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.

PUBLISHED Reserved 2026-05-07 | Published 2026-05-26 | Updated 2026-05-27 | Assigner GitHub_M




MEDIUM: 5.1CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:P/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N

Problem types

CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')

Product status

>= 2.49.0, < 3.5.3
affected

>= 3.6.0-rc.0, < 3.11.3
affected

References

github.com/...etheus/security/advisories/GHSA-fw8g-cg8f-9j28

github.com/...ommit/38f23b9075ced1de2b82d2dad8b2bebb1ecd5b7d

cve.org (CVE-2026-44903)

nvd.nist.gov (CVE-2026-44903)

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