5.3

CVE-2026-90990: checkmk gmbh checkmk CRLF Injection

CVSS: 5.3v4.0MediumDeferred
Published 22-09-2026Last modified 22-09-2026
Open JSON

Vulnerability summary

CVE-2026-90990 is a medium (CVSS 5.3) CRLF Injection vulnerability in checkmk gmbh checkmk. EPSS estimates a 0.42% chance of exploitation in the next 30 days, higher than 35.2% of scored vulnerabilities.

Overall risk
21/100
0100
Low · default modelHow is this calculated?
CVSS score
5.3/10
010
Medium · v4.0 (CVE.org)
EPSS score
0.42%
0%100%
Low · Change unavailable
KEVNot listedIn no KEV catalog
RansomwareNone recordedNo known use recorded
Public exploits0No public exploits recorded

Timeline

  1. 22-09-2026
    PublishedVulnerability first disclosed.
  2. 22-09-2026
    Last modifiedVulnerability information updated.

Description

Improper neutralization of newlines in filter values in the monitoring host and service list APIs in Checkmk <2.5.0p14 allows an authenticated user to inject additional Livestatus query headers, bypassing object visibility restrictions in count queries to infer information about hosts and services outside their contact groups and occupying web server and Livestatus workers for an attacker-controlled duration.

CVSS metrics

2 scores · 2 sources · 1 version

EPSS trend

Probability

0.42%

Chance of exploitation in the next 30 days

Percentile

35%

Versus all other CVEs

30-day change

Change unavailable

Change unavailable

23-09-202621-10-2026
EPSS score
0.42%

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

Checkmk gmbh1 product

1 vendor · 1 product

References

1 links