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VulnerabilityPublished Updated

CVE-2025-64999: Checkmk · Cross-site Scripting

Affects CheckmkSource CVE Database V5

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Not known to be exploited · CVSS 7.3 High : upgrade to 2.4.0p22 or 2.3.0p43 soon.

Data as of 29 Oct 2026, 19:04 UTC

CVSS 4.0 base score
7.3High
How severe the flaw is on the 0–10 CVSS scale.
EPSS
0.1% chance of exploitation in 30 days – higher than 6% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch
Available – fixed in 2.4.0p22, 2.3.0p43
CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:A/VC:H/VI:H/VA:H/SC:N/SI:L/SA:N

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 26 Feb 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 29 Oct 2026.

What to do

Upgrade Checkmk to 2.4.0p22 or 2.3.0p43.

Affected software

ProductAffectedFixed in
Checkmk GmbHCheckmkAffected
  • >=2.4.0 <2.4.0p22
Fixed in
  • 2.4.0p22
Checkmk GmbHCheckmkAffected
  • >=2.3.0 <2.3.0p43
Fixed in
  • 2.3.0p43
GitHubcheckmk/checkmkpkg:github/checkmk/checkmkOther threatsAffected
  • =2.4.0
  • =2.3.0
Fixed in–

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

If you cannot patch yet, limit the ability of untrusted users to manipulate host check outputs and educate users to be cautious with phishing links that may lead to Synthetic Monitoring HTML logs.

Description

Improper neutralization of input in Checkmk versions 2.4.0 before 2.4.0p22, and 2.3.0 before 2.3.0p43 allows an attacker that can manipulate a host's check output to inject malicious JavaScript into the Synthetic Monitoring HTML logs, which can then be accessed via a crafted phishing link.

References

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