8.5

CVE-2026-8833: checkmk gmbh checkmk Cross-site Scripting

CVSS: 8.5v4.0HighAnalyzed
AliasesUBUNTU-CVE-2026-8833
Published 08-06-2026Last modified 08-06-2026
Open JSON

Vulnerability summary

CVE-2026-8833 is a high (CVSS 8.5) Cross-site Scripting vulnerability in checkmk gmbh checkmk. EPSS estimates a 0.24% chance of exploitation in the next 30 days, higher than 14% of scored vulnerabilities.

Overall risk
34/100
0100
Medium · default modelHow is this calculated?
CVSS score
8.5/10
010
High · v4.0 (CVE.org)
EPSS score
0.24%
0%100%
Low · +0.10 pp in 30 days
KEVNot listedIn no KEV catalog
RansomwareNone recordedNo known use recorded
Public exploits0No public exploits recorded

Timeline

  1. 08-06-2026
    PublishedVulnerability first disclosed.
  2. 08-06-2026
    Last modifiedVulnerability information updated.

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.

CVSS metrics

5 scores · 3 sources · 2 versions

EPSS trend

Probability

0.24%

Chance of exploitation in the next 30 days

Percentile

14%

Versus all other CVEs

30-day change

+0.10 pp

From 0.14% on 21-09-2026

21-09-202621-10-2026
EPSS score
0.24%

Known exploited

Compare KEV catalogs

Not in any of the 3 tracked catalogs.

Public exploits

0 found

No public exploits indexed.

Weaknesses

CWE · root cause

Affected systems

Checkmk1 product
  • checkmkEOL2.2.0 | 2.2.0:b1 | 2.2.0:b2 | 2.2.0:b3 | 2.2.0:b4 | 2.2.0:b5 | 2.2.0:b6 | 2.2.0:b7 | 2.2.0:b8 | 2.2.0:i1 | 2.2.0:p1 | 2.2.0:p10 | 2.2.0:p11 | 2.2.0:p12 | 2.2.0:p13 | 2.2.0:p14 | 2.2.0:p15 | 2.2.0:p16 | 2.2.0:p17 | 2.2.0:p18 | 2.2.0:p19 | 2.2.0:p2 | 2.2.0:p20 | 2.2.0:p21 | 2.2.0:p22 | 2.2.0:p23 | 2.2.0:p24 | 2.2.0:p25 | 2.2.0:p26 | 2.2.0:p27 | 2.2.0:p28 | 2.2.0:p29 | 2.2.0:p3 | 2.2.0:p30 | 2.2.0:p31 | 2.2.0:p32 | 2.2.0:p33 | 2.2.0:p34 | 2.2.0:p35 | 2.2.0:p36 | 2.2.0:p37 | 2.2.0:p38 | 2.2.0:p39 | 2.2.0:p4 | 2.2.0:p40 | 2.2.0:p41 | 2.2.0:p42 | 2.2.0:p43 | 2.2.0:p44 | 2.2.0:p45 | 2.2.0:p46 | 2.2.0:p47 | 2.2.0:p5 | 2.2.0:p6 | 2.2.0:p7 | 2.2.0:p8 | 2.2.0:p9 | 2.3.0 | 2.3.0:b1 | 2.3.0:b2 | 2.3.0:b3 | 2.3.0:b4 | 2.3.0:b5 | 2.3.0:b6 | 2.3.0:p1 | 2.3.0:p10 | 2.3.0:p11 | 2.3.0:p12 | 2.3.0:p13 | 2.3.0:p14 | 2.3.0:p15 | 2.3.0:p16 | 2.3.0:p17 | 2.3.0:p18 | 2.3.0:p19 | 2.3.0:p2 | 2.3.0:p20 | 2.3.0:p21 | 2.3.0:p22 | 2.3.0:p23 | 2.3.0:p24 | 2.3.0:p25 | 2.3.0:p26 | 2.3.0:p27 | 2.3.0:p28 | 2.3.0:p29 | 2.3.0:p3 | 2.3.0:p30 | 2.3.0:p31 | 2.3.0:p32 | 2.3.0:p33 | 2.3.0:p34 | 2.3.0:p35 | 2.3.0:p36 | 2.3.0:p37 | 2.3.0:p38 | 2.3.0:p39 | 2.3.0:p4 | 2.3.0:p40 | 2.3.0:p41 | 2.3.0:p42 | 2.3.0:p43 | 2.3.0:p44 | 2.3.0:p45 | 2.3.0:p46 | 2.3.0:p47 | 2.3.0:p5 | 2.3.0:p6 | 2.3.0:p7 | 2.3.0:p8 | 2.3.0:p9 | 2.4.0 | 2.4.0:b1 | 2.4.0:b2 | 2.4.0:b3 | 2.4.0:b4 | 2.4.0:b5 | 2.4.0:b6 | 2.4.0:p1 | 2.4.0:p10 | 2.4.0:p11 | 2.4.0:p12 | 2.4.0:p13 | 2.4.0:p14 | 2.4.0:p15 | 2.4.0:p16 | 2.4.0:p17 | 2.4.0:p18 | 2.4.0:p19 | 2.4.0:p2 | 2.4.0:p20 | 2.4.0:p21 | 2.4.0:p22 | 2.4.0:p23 | 2.4.0:p24 | 2.4.0:p25 | 2.4.0:p26 | 2.4.0:p27 | 2.4.0:p28 | 2.4.0:p29 | 2.4.0:p3 | 2.4.0:p30 | 2.4.0:p4 | 2.4.0:p5 | 2.4.0:p6 | 2.4.0:p7 | 2.4.0:p8 | 2.4.0:p9 | 2.5.0 | 2.5.0:b1 | 2.5.0:b2 | 2.5.0:b3 | 2.5.0:p1 | 2.5.0:p2 | 2.5.0:p3 | 2.5.0:p4
Checkmk gmbh1 product
  • checkmkEOL≥ 2.5.0, < 2.5.0p5 | ≥ 2.4.0, < 2.4.0p31 | ≥ 2.3.0, < 2.3.0p48 | 2.2.0
Ubuntu1 product
  • check-mkAll versions (No fix recorded)

3 vendors · 3 products

References

3 links