---
id: CVE-2026-77021
title: >-
  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 se…
summary: >-
  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 se…
severity: medium
cvss: 5.3
cvssVector: 'CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N'
cwe:
  - CWE-409
vendor: Checkmk GmbH
product: Checkmk
affected:
  - Checkmk >= 2.5.0 < 2.5.0p14
  - Checkmk >= 2.4.0 < 2.4.0p37
  - Checkmk >= 2.3.0 < 2.3.0p51
  - Checkmk 2.2.0
published: '2026-09-21'
updated: '2026-09-21'
sourceUpdated: '2026-09-21T20:17:32.393'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-77021'
references:
  - url: 'https://checkmk.com/werk/22116'
    label: security@checkmk.com
tags:
  - nvd
  - cve.org
ssvc:
  exploitation: none
  automatable: 'no'
  technicalImpact: partial
  timestamp: '2026-09-21T14:40:45.554408Z'
cvssSource: cna
ingestedAt: '2026-09-21T11:35:54.432Z'
epss: 0.00382
epssPercentile: 0.29477
---

## Overview

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.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.