Medium severity · published Jun 8, 2026
CVE-2026-9549
Fix XSS in service discovery active check output
4.8
CVSS
0.1%
EPSS
No
On KEV
Description
Stored cross-site scripting in the service discovery active check output in Checkmk <2.5.0p5, <2.4.0p31, <2.3.0p48, and all 2.2.0 versions allows an administrator who can configure active or custom checks to inject malicious HTML or JavaScript into check output that executes in the browser of an admin or a user with host read permissions when they run the check on the service discovery page.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:H/UI:R/S:C/C:L/I:L/A:N
Attack vector
Network
Complexity
Low
Privileges
High
User interaction
Required
Confidentiality
Low
Integrity
Low
Availability
None
Scope
Changed
Exploitation
Is it being used?
Exploit prediction (EPSS)0.1% · higher than 4% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
CH
Checkmk · Checkmk GmbH
2.5.0 before 2.5.0p5; 2.4.0 before 2.4.0p31; 2.3.0 before 2.3.0p48; 2.2.0 · source: vendor, NVD
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-9549
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-9549
Vendor Advisory
https://checkmk.com/werk/17993
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