CVE-2026-77021 PUBLISHED

Missing decompression size limit in agent receiver allows memory exhaustion via push agent data

Assigner: Checkmk
Reserved: 20.08.2026 Published: 21.09.2026 Updated: 21.09.2026

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.

Metrics

CVSS 4.0

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
CVSS Score: 5.3

Exploitability Metrics		Vulnerable System Impact Metrics		Subsequent System Impact Metrics
Attack Vector	Network	Confidentiality	None	Confidentiality	None
Attack Complexity	Low	Integrity	None	Integrity	None
Attack Requirements	None	Availability	Low	Availability	None
Privileges Required	Low
User Interaction	None

CVSS 4.0

Product Status

Vendor	Checkmk GmbH
Product	Checkmk
Versions	Default: unaffected affected from 2.5.0 to 2.5.0p14 (excl.) affected from 2.4.0 to 2.4.0p37 (excl.) affected from 2.3.0 to 2.3.0p51 (excl.) Version 2.2.0 is affected

Credits

Sven Jäger (SySS GmbH) reporter

References

https://checkmk.com/werk/22116

Problem Types

CWE-409: Improper Handling of Highly Compressed Data (Data Amplification) CWE

Impacts

CAPEC-197: Exponential Data Expansion