Medium severity · published Sep 21, 2026
CVE-2026-77021
Missing decompression size limit in agent receiver allows memory exhaustion via push agent data
5.3
CVSS
0.4%
EPSS
No
On KEV
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.
Exploitation
Is it being used?
Exploit prediction (EPSS)0.4% · higher than 32% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
CH
Checkmk · Checkmk GmbH
2.5.0 before 2.5.0p14; 2.4.0 before 2.4.0p37; 2.3.0 before 2.3.0p51; 2.2.0 · source: vendor
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-77021
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-77021
checkmk.com
https://checkmk.com/werk/22116
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