CVE-2026-15227

In Checkmk versions <2.4.0p23, <2.3.0p45, and 2.2.0, there is a vulnerability related to the exposure of the session signing secret. An administrator of a remote site with config sync enabled can hijack sessions on the central site by forging session cookies.

Missing authorization in Checkmk versions <2.5.0p12, <2.4.0p36, <2.3.0p50 and all 2.2.0 versions allows an authenticated user who knows the ID of a background job to view that job's status and results.

Improper authentication in the agent receiver of Checkmk before 2.5.0p10 allows an unauthenticated remote attacker to bypass mutual TLS client certificate verification of relay endpoints by supplying a fixed placeholder identity in the request URL, resulting in limited impact on integrity and availability. Only Cloud, Ultimate, and Ultimate MT editions are affected.

An incorrect authorization vulnerability in frozen BI aggregations in Checkmk (versions <2.5.0p2, <2.4.0p29, <2.3.0p47, and all 2.2.0) allows an authenticated user with restricted host and service visibility to learn the names and existence of hosts and services they are not authorized to see.

Improper permission enforcement in Checkmk versions 2.5.0 before 2.5.0p9, 2.4.0 before 2.4.0p34, 2.3.0 before 2.3.0p49, and 2.2.0 (EOL) allows users without permissions to view and modify BI packs and rules.

A privilege escalation vulnerability in Checkmk allows a local unprivileged user to execute arbitrary commands as root by starting a process crafted to look like a SAP HANA instance. The mk_sap_hana agent plugin, running as root, derives instance identifiers from the process list and uses them to build a command executed with elevated privileges.

Stored XSS in service discovery active check output in Checkmk <2.5.0p5, <2.4.0p31, <2.3.0p48, and all 2.2.0 allows an admin to inject malicious HTML/JavaScript into check output.

Improper neutralization of HTML-encoded characters in URL validation in Checkmk <2.5.0p5, <2.4.0p31, <2.3.0p48, and all 2.2.0 allows an authenticated user to bypass URL validation and inject malicious URLs like javascript: URIs, leading to XSS.

Stored XSS in global settings change log in Checkmk <2.5.0p5, <2.4.0p31, <2.3.0p48, and all 2.2.0 allows an admin to store malicious HTML/JavaScript in changelog messages.

Checkmk before version 2.5.0p5 has an incorrect authorization vulnerability in the User Messages dashboard widget. Message-fetching endpoints return the dashboard creator's messages instead of the viewer's, allowing an attacker with a valid public dashboard share token to read the issuer's personal messages.