How to Fix CVE-2026-33276: Checkmk (Bundle Sibling)
*By Sai Kiran Pandrala*
Last verified: 2026-05-25
| Severity | CVSS 8.6, High |
|---|---|
| Actively exploited? | No |
| Affected | Checkmk Gmbh Checkmk (2.5.0b1 < 2.5.0b2) |
| Fixed in | Same patched build as CVE-2026-3466 |
| Type (CWE) | CWE-79: CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') |
CVE-2026-33276 is a sibling vulnerability in the same Checkmk Gmbh Checkmk advisory bundle as CVE-2026-3466. The same patched build closes every CVE in the bundle, so the remediation procedure for CVE-2026-33276 matches the primary write-up.
What is different about CVE-2026-33276?
Stored cross-site scripting (XSS) in Checkmk 2.5.0 (beta) before 2.5.0b2 allows authenticated users with permission to create hosts or services to execute arbitrary JavaScript in the browsers of other users performing searches in the Unified Search feature.
Impact is consistent with the bundle: execution of attacker-controlled JavaScript in a victim's browser. The patched build closes every code path in the advisory in one update.
How to fix CVE-2026-33276
Apply the patched build per the primary write-up: How to Fix CVE-2026-3466.
For a quick check, confirm the running version of Checkmk:
# Confirm the installed version via your package manager
dpkg -l | grep -i checkmk # Debian/Ubuntu
rpm -qa | grep -i checkmk # RHEL/CentOS/Rocky
Frequently asked questions
Is CVE-2026-33276 being actively exploited?
Not at the time of writing. It is not listed in CISA's Known Exploited Vulnerabilities catalog. That status can change, so monitor the vendor advisory and the KEV catalog if the system is exposed.
How severe is CVE-2026-33276?
CVSS rates it 8.6 (High). Use that score to set your patch priority alongside the other items in your queue.
Do I have to take Checkmk offline to apply the patch?
It depends on the deployment. High-availability or clustered installs can usually patch one node at a time with no full outage. Standalone installs typically need a short restart. Always follow the vendor's documented upgrade steps.
What if my vulnerability scanner still flags CVE-2026-33276 after I patch?
Re-run the scan after a service restart, then confirm the scanner's plugin set is up to date. Some scanners detect by banner version only and lag the official fix metadata by a release.
References
- Official vendor advisory: https://checkmk.com/werk/19525
- NVD entry: https://nvd.nist.gov/vuln/detail/CVE-2026-33276
- CISA KEV catalog: https://www.cisa.gov/known-exploited-vulnerabilities-catalog
- Primary write-up: How to Fix CVE-2026-3466
*Written by Sai Kiran Pandrala. Last verified 2026-05-25. Part of the Checkmk Gmbh Checkmk advisory bundle. Full procedure at how-to-fix-cve-2026-3466.*