CVE-2021-40906

6.1 mediumEPSS 1.0%

CheckMK Raw Edition software (versions 1.5.0 to 1.6.0) does not sanitise the input of a web service parameter that is in an unauthenticated zone. This Reflected XSS allows an attacker to open a backdoor on the device with HTML content and interpreted by the browser (such as JavaScript or other client-side scripts) or to steal the session cookies of a user who has previously authenticated via a man in the middle. Successful exploitation requires access to the web service resource without authentication.

Severity

CVSS 3.1

6.1 medium

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

EPSS: 1.0% chance of exploitation in the next 30 days; higher than 62% of CVEs (scores of 2026-10-31)
CWE: CWE-79
Published: 2022-03-25
Modified: 2026-07-09
Record from: the NVD, synced 2026-10-19

Affected

checkmk:checkmk
tribe29:checkmk

References

https://github.com/Edgarloyola/CVE-2021-40906
https://github.com/Edgarloyola/CVE-2021-40906

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