Checkmk: Mehrere Schwachstellen ermöglichen Cross-Site Scripting
WID-SEC-2026-0928 · first 31.03.2026 · updated 01.04.2026 · CVSS 9,0
What it is about
Checkmk ist eine IT-Monitoring-Software. Ein Angreifer kann mehrere Schwachstellen in Checkmk ausnutzen, um einen Cross-Site Scripting Angriff durchzuführen.
Under what conditions?
The BSI does not name any particular preconditions. Exploitable remotely according to the BSI.
What can happen in the worst case
An attacker could use the vulnerability to
- einen Cross-Site Scripting Angriff durchzuführen
Am I affected?
Affected according to the BSI:
- Checkmk Checkmk <2.6.0b1
- Checkmk Checkmk <2.5.0b2
The installed version is usually shown under “Help → About” or in the device’s admin interface.
What helps?
Update to at least:
- Checkmk Checkmk 2.6.0b1
- Checkmk Checkmk 2.5.0b2
Is the vulnerability already being exploited?
None of the CVEs is in the CISA catalogue of exploited vulnerabilities. That does not mean there are no attacks, only that none are documented.
Information and sources
- Original BSI advisory (WID)
- CheckMK Werk 19525 vom 2026-03-30 checkmk.com
- CheckMK Werk 19526 vom 2026-03-30 checkmk.com
CVE: CVE-2026-20915, CVE-2026-33276
Source: BSI warning and information service (CERT-Bund); CISA. The assessment of the conditions is my reading of the BSI text; the external pages are in their original language.