CVE-2026-77021
📛 CVE Title
Missing decompression size limit in agent receiver allows memory exhaustion via push agent data
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.
Overview
- State
- PUBLISHED
- Assigner (CNA)
- Checkmk
- CVSS severity
- MEDIUM
- CVSS score
- 5.3 / 10
- CVSS vector
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- Effective score
- 5.3 / 10 MEDIUM source: CNA overview
- CWE(s)
-
CWE-409 - Reserved
- 2026-08-20
- Published
- 2026-09-21 10:57 UTC
- Last updated
- 2026-09-21 19:40 UTC
- Source
- https://raw.githubusercontent.com/CVEProject/cvelistV5/main/cves/2026/77xxx/CVE-2026-77021.json
NVD triage scoring NVD CVE 2.0
Layer NVD adds on top of the CNA's CVE record — published / last-modified timestamps, exploitability / impact subscores, and the FIRST.org EPSS probability that this CVE will be exploited in the wild in the next 30 days.
- NVD published
- 2026-09-21 11:17:12 UTC
- NVD last modified
- 2026-09-21 20:17:32 UTC
NVD / KEV / EPSS data refreshed 2026-09-22 03:38 UTC. Re-run the 🛰 Backfill from NVD button above to refresh.
European Union Vulnerability Database ENISA EUVD
ENISA's official EU repository for curated vulnerability intelligence. Carries a separate identifier (EUVD-YYYY-NNNN) and frequently exposes an earlier-published description + CVSS than NVD does.
- EUVD ID
-
EUVD-2026-83883 - Assigner
- Checkmk
- Published
- Sep 21, 2026, 10:57:37 AM
- Updated
- Sep 21, 2026, 7:40:26 PM
- EUVD base score (CVSS 4.0)
-
5.3 / 10
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 - EUVD-reported EPSS
- 0.0000
- Vendors
- Checkmk GmbH
- Products
-
Checkmk (2.4.0 <2.4.0p37)Checkmk (2.3.0 <2.3.0p51)Checkmk (2.5.0 <2.5.0p14)Checkmk (2.2.0)
- Aliases
-
GHSA-5q8h-fhcg-2395
ENISA 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.
EUVD references (1)
Affected products (1)
| Vendor | Product | Versions | Platforms |
|---|---|---|---|
| Checkmk GmbH | Checkmk |
2.5.0 (affected),
2.4.0 (affected),
2.3.0 (affected),
2.2.0 (affected)
|
— |
Vendor references (1)
References embedded in the original CVE record by the assigning CNA.
- https://checkmk.com/werk/22116 vendor-advisory
Web references (0)
DuckDuckGo results ranked by threat-intel / vendor advisory domains. Generated by the 🔎 Find references (web) button above — same flow as the Remediations search.
No web references attached yet.
NVD-tagged references (1)
Reference list NVD curates from the CNA record, vendor advisories, and third-party reports. The tag chips below are NVD's analyst-assigned categories.
- https://checkmk.com/werk/22116 security@checkmk.com
Remediations (10)
-
web:blogs.oracle.com
For more information about the Critical Patch Update program, see the security vulnerability remediation practices page located on the Oracle Trust Center.
2026-09-22 17:10 UTC -
web:blogs.oracle.com
As a follow-up to our recent post, Accelerating Vulnerability Detection and Response, Oracle is announcing the start date and cadence for monthly Critical Security Patch Updates (CSPUs). Beginning May 28, 2026 , Oracle will deliver a Critical Security Patch Update (CSPU) each month.
2026-09-22 17:10 UTC -
web:cvetodo.com
CVE-2026-77021 is a CVSS 5.3 medium-severity vulnerability in Checkmk. Full technical analysis, mitigations , and exploit status — updated in real time.
2026-09-22 17:10 UTC -
web:senserva.com
Every Microsoft security patch (KB) and the CVEs it fixes, with severity, CVSS, and CISA KEV status. Cross-linked to the CVE reference.
2026-09-22 17:10 UTC -
web:support.sap.com
SAP security Patch Day Bulletin This post shares the information on security notes that remediate vulnerabilities discovered in SAP products. SAP strongly recommends that the customer visits the support portal and applies patches on priority to protect their SAP landscape. On 9th of June 2026 , SAP security patch day saw the release of 15 new security notes.
2026-09-22 17:10 UTC -
web:vulners.com
CVE-2026-77021 🗓️ 21 Sep 2026 03:57:37 Reported by Checkmk Type cve 🔗 web.nvd.nist.gov 👁 6 Views
2026-09-22 17:10 UTC -
web:www.nist.gov
NIST maintains the National Vulnerability Database (NVD), a repository of information on software and hardware flaws that can compromise computer security. This is a key piece of the nation's cybersecurity infrastructure.
2026-09-22 17:10 UTC -
web:www.oracle.com
This Critical Patch Update contains 1448 new security patches across the product families listed below. Please note that a My Oracle Support (MOS) note summarizing the content of this Critical Patch Update and other Oracle Software Security Assurance activities is located at July 2026 Critical Patch Update: Executive Summary and Analysis.
2026-09-22 17:10 UTC -
web:www.oracle.com
Additional CVEs addressed are: The patch for CVE - 2026 -34481 also addresses CVE - 2026 -34477, CVE - 2026 -34478, CVE - 2026 -34479, and CVE - 2026 -34480. Oracle Fusion Middleware Risk Matrix This Critical Security Patch Update contains 106 new security patches for Oracle Fusion Middleware. 53 of these vulnerabilities may be remotely exploitable without authentication, i.e., may be exploited over a ...
2026-09-22 17:10 UTC -
web:www.rapid7.com
CVE-2026-77021 : Checkmk GmbH Checkmk: Improper handling of highly compressed data (data amplification) in Checkmk <2.5.0p14, <2.4.0p37, <2.3.0p51 and 2.2.0…. View severity, references, and remediation details from Rapid7.
2026-09-22 17:10 UTC
AI Forensic Analysis
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Raw JSON
The full cvelistV5 record. Download as CVE-2026-77021.json.
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