CVE-2025-39666: Local privilege escalation in Checkmk 2.2.0 (EOL), Checkmk 2.3.0 before 2.3.0p46, Checkmk 2.4.0 before 2.4.0p2

Routine

HIGH 7.3DOWNGRADE

CVE-2025-39666 is a high-severity flaw (CVSS 7.3) affecting checkmk. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Local privilege escalation in Checkmk 2.2.0 (EOL), Checkmk 2.3.0 before 2.3.0p46, Checkmk 2.4.0 before 2.4.0p25, and Checkmk 2.5.0 (beta) before 2.5.0b3 allows a site user to escalate their privileges to root, by manipulating files in the site context that are processed when the `omd` administrative command is run by root.

Why this priority

High severity

No fix is published yet: follow the downgrade or mitigation steps.

Risk facts

CVSS score	7.3 (High)
Attack vector	Local
Attack complexity	Low
Privileges needed	Low
User interaction	Required
EPSS exploit chance	0.1% (top 98%)
CISA exploited list	No
Weakness	CWE-426, CWE-829
Published	2026-04-07
Last modified	2026-10-12

Publisher (CNA): Checkmk GmbH · Vendor: checkmk

Last updated 2026-10-12 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-04-07 13:16 UTCPublished CVE record published
2026-10-12 22:10 UTCUpdated Record last modified

checkmk checkmk DOWNGRADE

Affected: 2.2.0 · 2.2.0 b1 · 2.2.0 b2 · 2.2.0 b3 · 2.2.0 b4 · 2.2.0 b5 · 2.2.0 b6 · 2.2.0 b7

Fixed in: no fixed release known

Safe to downgrade to: a release before 2.2.0

1. Check installed version

apt-cache policy checkmk || rpm -q checkmk || checkmk --version

2. No fixed release: DOWNGRADE to a release before 2.2.0 (Debian / Ubuntu)

apt-cache madison checkmk sudo apt install checkmk=<VERSION_BEFORE_2.2.0> sudo apt-mark hold checkmk

2. No fixed release: DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list checkmk sudo dnf downgrade checkmk-<VERSION_BEFORE_2.2.0> sudo dnf versionlock add checkmk

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2025-39666?

checkmk: downgrade or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2025-39666 being exploited?

CVE-2025-39666 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2025-39666 affect?

CVE-2025-39666 affects checkmk. Severity is high (CVSS 7.3). Local privilege escalation in Checkmk 2.2.0 (EOL), Checkmk 2.3.0 before 2.3.0p46, Checkmk 2.4.0 before 2.4.0p25, and Checkmk 2.5.0 (beta) before 2.5.0b3 allows a site user to escalate their privileges to root, by manipulating files in the s

How urgent is CVE-2025-39666?

Priority 26/100. High severity

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References

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