CVE-2023-40577: Alertmanager UI is vulnerable to stored XSS via the /api/v1/alerts endpoint

Severity: medium (CVSS 5.4 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.6% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2023-08-25 · updated 2026-06-17
Weakness: CWE-79

Description

Alertmanager handles alerts sent by client applications such as the Prometheus server. An attacker with the permission to perform POST requests on the /api/v1/alerts endpoint could be able to execute arbitrary JavaScript code on the users of Prometheus Alertmanager. This issue has been fixed in Alertmanager version 0.2.51.

Affected products

Debian Linux: 10.0
prometheus alertmanager: 0.25.0

References

https://github.com/prometheus/alertmanager/security/advisories/GHSA-v86x-5fm3-5p7j
https://lists.debian.org/debian-lts-announce/2023/10/msg00011.html
https://github.com/prometheus/alertmanager/security/advisories/GHSA-v86x-5fm3-5p7j
https://lists.debian.org/debian-lts-announce/2023/10/msg00011.html

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