5.3

CVE-2026-77021: checkmk gmbh checkmk

CVSS: 5.3v4.0MediumDeferred
Published 21-09-2026Last modified 21-09-2026
Open JSON

Vulnerability summary

CVE-2026-77021 is a medium (CVSS 5.3) vulnerability in checkmk gmbh checkmk. EPSS estimates a 0.38% chance of exploitation in the next 30 days, higher than 30.9% 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
0.38%
0%100%
Low · Change unavailable
KEVNot listedIn no KEV catalog
RansomwareNone recordedNo known use recorded
Public exploits0No public exploits recorded

Timeline

  1. 21-09-2026
    PublishedVulnerability first disclosed.
  2. 21-09-2026
    Last modifiedVulnerability information updated.

Description

Improper handling of highly compressed data (data amplification) in Checkmk <2.5.0p14, <2.4.0p37, <2.3.0p51 and 2.2.0 (EOL) allows an attacker who controls a host registered for push mode to exhaust the memory of the agent receiver by sending a small zlib compressed payload that decompresses to an arbitrary size.

CVSS metrics

2 scores · 2 sources · 1 version

EPSS trend

Probability

0.38%

Chance of exploitation in the next 30 days

Percentile

31%

Versus all other CVEs

30-day change

Change unavailable

Change unavailable

22-09-202621-10-2026
EPSS score
0.38%

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
  • checkmkEOL≥ 2.5.0, < 2.5.0p14 | ≥ 2.4.0, < 2.4.0p37 | ≥ 2.3.0, < 2.3.0p51 | 2.2.0

1 vendor · 1 product

References

1 links