What’s Vulnerable › Vulnerabilities

CVE-2025-64999: Cross-site scripting in HTML logs of Synthetic Monitoring test services

• Severity: medium (CVSS 5.4 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.2% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-02-26 · updated 2026-06-17
• Weakness: CWE-79

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

• Checkmk GmbH Checkmk: 2.3.0, 2.3.0-b1, 2.3.0-b2, 2.3.0-b3, 2.3.0-b4, 2.3.0-b5 (+71)

References

• https://checkmk.com/werk/19238
• https://github.com/sbaresearch/advisories/tree/e72ce9bb6b9ffffc1fc35e4d8152ad153293c851/2025/SBA-ADV-20251118-01_Checkmk_Cross_Site_Scripting

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