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CheckmkApplication

CVE-2025-65000

MEDIUM · 5.3 CVSS v3.1 Published 2025-12-18
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
62/100
Remediation priority · Elevated
Remotely reachable No privileges Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
SSH private keys of the "Remote alert handlers (Linux)" rule were exposed in the rule page's HTML source in Checkmk <= 2.4.0p18 and all versions of Checkmk 2.3.0. This potentially allowed unauthorized triggering of predefined alert handlers on hosts where the handler was deployed.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

SSH private keys associated with 'Remote alert handlers (Linux)' rules were embedded in plaintext within the HTML source of the rule configuration page in Checkmk versions 2.3.0 and <= 2.4.0p18. This exposure allows any user or automated process with access to view the page source to retrieve the private keys and authenticate to remote systems configured as alert handler targets.

MitigationUpgrade Checkmk to version 2.4.0p19 or later to receive the vendor patch. Additionally, rotate all SSH private keys that were used in 'Remote alert handlers (Linux)' rules during the affected versions to prevent continued risk from keys that may have been exfiltrated.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
CheckmkApplication
Affected:= 2.2.0= 2.3.0= 2.4.0

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
Low
Integrity
None
Availability
None

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Identify installed Checkmk version
    Run 'omd version' or check /omd/versions/version file to determine the exact Checkmk version running in your environment
    Affected if Version is 2.2.0, 2.3.0, or any 2.4.0 version up to and including 2.4.0p18 (the raw version string '2.4.0' without a patch number also falls within the affected range)
  2. Locate Remote alert handlers (Linux) rules
    Access the Checkmk web interface (WATO), navigate to 'Setup > Events > Alert handlers' or check configuration files in ~/etc/checkmk/mkalertd.d/ for rules with type 'Remote alert handlers (Linux)'
    Affected if Any 'Remote alert handlers (Linux)' rules exist in the environment
  3. Inspect HTML source for exposed SSH private keys
    Open the rule configuration page for any Remote alert handlers (Linux) rule in the web UI, then view the page source (right-click > View Page Source or use browser dev tools), search for '-----BEGIN' to locate any SSH private key material
    Affected if Private key content beginning with '-----BEGIN' is visible in plaintext within the HTML source of the rule configuration page

You are affected if your Checkmk version is 2.2.0, 2.3.0, or any 2.4.0 version up to 2.4.0p18 AND you have configured any Remote alert handlers (Linux) rules that contain SSH private keys, as these keys would be exposed in the HTML source of the configuration page.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Upgrade Checkmk to version 2.4.0p19 or later to receive the vendor patch. Additionally, rotate all SSH private keys that were used in 'Remote alert handlers (Linux)' rules during the affected versions to prevent continued risk from keys that may have been exfiltrated.

Recommended fix Moderate confidence

Checkmk 2.4.0p18 or later (2.3.0 users should upgrade to 2.4.0p18+, 2.2.0 users should upgrade to a supported 2.4.0pX version)

  1. Backup your current Checkmk configuration and data before upgrading
  2. Review the Checkmk 2.4.0p18 release notes at checkmk.com for any important changes
  3. Download Checkmk 2.4.0p18 or later from the official Checkmk download site
  4. If using a standalone setup, follow the standard upgrade procedure for your installation type (raw, beta, or enterprise edition)
  5. If using a distributed setup with remote sites, upgrade the central site first, then upgrade each remote site
  6. After upgrade, verify the 'Remote alert handlers (Linux)' rule no longer exposes SSH private keys in the HTML source
  7. Test that alert handlers function correctly after the upgrade
Caveat Review release notes for any breaking changes between 2.2.0/2.3.0 and 2.4.0p18

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Checkmk Scoped from the published advisory
  • Consultation3.0 h
  • Implementation6.0 h
  • Testing3.0 h
  • Review / QA2.0 h
14.0 hours of engineering $2,490
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2025-65000 in production — separate from our analysis above.

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data