Vulnerability · Published Feb 26, 2026 · Assigned by Checkmk
CVE-2025-64999Cross-site scripting in HTML logs of Synthetic Monitoring test services
High 7.3
In plain English
A high-severity cross-site scripting in Checkmk from Checkmk GmbH. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.2% (higher than 6% of all known vulnerabilities).
Severity (CVSS 4.0)7.3High
Exploit odds (30 days)0.2%top 93.8% of all CVEs
Exploited in the wildNo reportsCISA SSVC: poc
Attack toolingNoneno public tooling known
Official 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.
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| Checkmk GmbH | Checkmk | 2.4.0 – before 2.4.0p222.3.0 – before 2.3.0p43 |
Weakness: CWE-79 · Vector: 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