CVE-2021-40906

Name: CVE-2021-40906
Creator: NVD / NIST
Published: 2022-03-25T23:15:08.287+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

MEDIUMCVSS 6.1/10EPSS 0.99%

Last modified Jun 17, 2026

CVE-2021-40906 is a medium-severity vulnerability rated 6.1/10 on the CVSS scale. 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. EPSS estimates a 0.99% chance of exploitation in the next 30 days.

Description

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.

Metrics

CVSS 3.1

6.1/10

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

EPSS Probability

0.99%

58.0th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-79

Affected Software

Vendor	Product	Versions
Checkmk	Checkmk	>= 1.5.0, < 1.6.0
Checkmk	Checkmk	1.6.0
Tribe29	Checkmk	1.6.0b10
Tribe29	Checkmk	1.6.0b11
Tribe29	Checkmk	1.6.0p10
Tribe29	Checkmk	1.6.0p17
Tribe29	Checkmk	1.6.0p18

References

http://checkmk.comProduct
https://github.com/Edgarloyola/CVE-2021-40906Third Party Advisory
http://checkmk.comProduct
https://github.com/Edgarloyola/CVE-2021-40906Third Party Advisory

Timeline

Published: Mar 25, 2022
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2021-40906?

How severe is CVE-2021-40906?

CVE-2021-40906 has a CVSS score of 6.1/10 (MEDIUM severity). The EPSS model estimates a 0.99% probability of exploitation in the next 30 days.

How do I fix CVE-2021-40906?

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.

Are you affected by CVE-2021-40906?

Run a free Strix scan to check your systems for this vulnerability.

Scan your code now

Source: NVD / NIST