CVE-2026-8833 | BDVDB-2026-338403 Detail

CheckmkCheckmk

Description#

Improper neutralization of HTML-encoded characters in the URL validation function in Checkmk <2.5.0p5, <2.4.0p31, <2.3.0p48, and all 2.2.0 versions allows an authenticated user to bypass URL validation and inject malicious URLs such as javascript: URIs, resulting in cross-site scripting when another user interacts with the crafted link.

Impact#

CAPEC-63: Cross-Site Scripting (XSS)

Weaknesses#

CWE-79 Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')

References#

https://checkmk.com/werk/20002

Exploit#

No public exploit known

History#

Version 12026-06-08Record published in the CVE List.

Published

Published: 2026-06-08
Last modified: 2026-06-08

Vendor information

Vendor: Checkmk
Product: Checkmk

All Checkmk vulnerabilities

Score

8.5 High

EPSS

less than 1%, Very Low

Estimated chance of exploitation in the next 30 days. EPSS percentile: 3.4.

KEV

Not listed in the CISA Known Exploited Vulnerabilities catalog.

Impact

Cross-Site Scripting

Action

No specific action is recorded in the source data. Check the references for vendor guidance.

Affected Systems

Vulnerable
>= 2.5.0 and < 2.5.0p5
Fixed
2.5.0p5
Vulnerable
>= 2.4.0 and < 2.4.0p31
Fixed
2.4.0p31
Vulnerable
>= 2.3.0 and < 2.3.0p48
Fixed
2.3.0p48
Vulnerable
2.2.0
Fixed
Not stated

Scoring System

CVSS v4.0

8.5 High

CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:A/VC:H/VI:H/VA:H/SC:N/SI:L/SA:N

Metric breakdown
Attack Vector	Network
Attack Complexity	Low
Attack Requirements	None
Privileges Required	Low
User Interaction	Active
Vulnerable System Confidentiality	High
Vulnerable System Integrity	High
Vulnerable System Availability	High
Subsequent System Confidentiality	None
Subsequent System Integrity	Low
Subsequent System Availability	None

CVSS v3.1

Not available

CVSS v3.0

Not available

CVSS v2

Not available

Source: CVE List v5 (record); CISA KEV (kev, action); FIRST EPSS (epss).