CVE-2021-36563

What it is

The CheckMK management web console (versions 1.5.0 to 2.0.0) does not sanitise user input in various parameters of the WATO module. This 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), the XSS payload will be triggered when the user accesses some specific sections of the application. In the same sense a very dangerous potential way would be when an attacker who has the monitor role (not administrator) manages to get a stored XSS to steal the secretAutomation (for the use of the API in administrator mode) and thus be able to create another administrator user who has high privileges on the CheckMK monitoring web console. Another way is that persistent XSS allows an attacker to modify the displayed content or change the victim's information. Successful exploitation requires access to the web management interface, either with valid credentials or with a hijacked session.

At a glance

Exploitability

Can be exploited over the network with a low-privilege account, but needs a user to act. Limited direct impact.

Exploit odds

1.7% chance of exploitation in the next 30 days (EPSS).

Fix

A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

1. 2021-07-26 18:15 UTC PublishedDisclosed publicly on CVE.org and NVD
2. 2026-06-17 03:58 UTC Last updatedMost recent change to the record

Why it ranks here

• Exploited in the wild: no, CISA does not list it.
• Exploit odds: 1.7% in the next 30 days (EPSS).
• Severity: 5.4 MEDIUM (CVSS).
• Fix: a patch or advisory is linked.

Details

Published

2021-07-26 18:15 UTC

Last modified

2026-06-17 03:58 UTC

Exploit probability

1.7% · EPSS, next 30 days

Weakness

CWE-79 · Cross-site scripting

Record status

Modified

Affected

• Checkmk ≤ 2.0.0

Attack profile CVSS 3.1 · 5.4

Attack vector

Network

Complexity

Low

Privileges needed

Low

User interaction

Required

Scope

Changed

Confidentiality

Low

Integrity

Low

Availability

None

Is it in your code?

Hand this to your coding agent. It searches your project for the affected products and checks versions. Nothing leaves your machine.

Read https://cve-list.com/agent/cve/CVE-2021-36563.md and follow it. Check whether this project is affected by CVE-2021-36563. Read only. Don't change anything and don't upload my code. Tell me yes, no or not sure, with the file as proof.

Copy as ticket · More options · Status badge