What’s Vulnerable › Vulnerabilities
CVE-2026-77021: Missing decompression size limit in agent receiver allows memory exhaustion via push agent data
- Severity: medium (CVSS 5.3 v4.0)
- Exploited in the wild: not listed in CISA KEV
- EPSS: 0.4% probability of exploitation in the next 30 days
- Public exploit or detection template: none known
- Published: 2026-09-21 · updated 2026-09-21
- Weakness: CWE-409
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.
Affected products
- Checkmk GmbH Checkmk: from 2.5.0 before 2.5.0p14; from 2.4.0 before 2.4.0p37; from 2.3.0 before 2.3.0p51; 2.2.0 — fixed in 2.3.0p51, 2.4.0p37, 2.5.0p14
How to fix
Upgrade to a fixed version: Checkmk GmbH Checkmk 2.3.0p51, 2.4.0p37, 2.5.0p14. Check the vendor advisory for mitigations.
References
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