Root access via vulnerable Checkmk versions; widely used IT monitoring software.
CVE-2025-39666
Local privilege escalation in Checkmk allows root via site-context file manipulation.
Is CVE-2025-39666 being exploited?
Not confirmed. CVE-2025-39666 does not appear in CISA's Known Exploited Vulnerabilities catalog, which records only exploitation that has been observed and reported publicly. That is evidence of absence of a report, not evidence the flaw is unattacked. EPSS currently estimates a 0.12% probability of exploitation in the next 30 days.
How severe is CVE-2025-39666?
CVE-2025-39666 is rated Critical with a CVSS score of 9.3. Severity describes how bad exploitation would be, not how likely it is: pair it with exploitation evidence before deciding what to patch first.
Is there a patch for CVE-2025-39666?
Yes. A fix has been recorded for CVE-2025-39666. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2025-39666 affect?
CVE-2025-39666 affects Checkmk 2.2.0 (EOL), Checkmk 2.3.0 before 2.3.0p46, Checkmk 2.4.0 before 2.4.0p25, Checkmk 2.5.0 beta before 2.5.0b3. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2025-39666?
Upgrade to patched release; restrict site-user rights.
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Site user can escalate to root, compromising the Checkmk server and monitoring data.
Immediate action required
- affected2.2.0
- affected>= 2.3.0 and < 2.3.0p46
- affected>= 2.4.0 and < 2.4.0p25
- affected>= 2.5.0b1 and < 2.5.0b3
As published in the CVE Program record. A version outside these ranges is not a statement that it is unaffected — vendors sometimes understate a range, and distribution-backported builds carry upstream numbers that do not reflect what was patched into them.