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CVE-2026-9549

MEDIUMCVSS 4.8/10EPSS 0.14%

Last modified

CVE-2026-9549 is a medium-severity vulnerability rated 4.8/10 on the CVSS scale. 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.. EPSS estimates a 0.14% chance of exploitation in the next 30 days.

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.

Metrics

CVSS 3.1
4.8/10

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

CVSS 4.0
4.8/10

CVSS:4.0/AV:N/AC:L/AT:N/PR:H/UI:P/VC:N/VI:L/VA:N/SC:N/SI:L/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

EPSS Probability
0.14%

4.0th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

Affected Software

VendorProductVersions
CheckmkCheckmk2.2.0
CheckmkCheckmk2.3.0
CheckmkCheckmk2.4.0
CheckmkCheckmk2.5.0

References

Timeline

Published
Last Modified
Status
Analyzed

Frequently Asked Questions

What is CVE-2026-9549?
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.
How severe is CVE-2026-9549?
CVE-2026-9549 has a CVSS score of 4.8/10 (MEDIUM severity). The EPSS model estimates a 0.14% probability of exploitation in the next 30 days.
How do I fix CVE-2026-9549?
Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

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Source: NVD / NIST