{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-77021","assignerOrgId":"f7d6281c-4801-44ce-ace2-493291dedb0f","state":"PUBLISHED","assignerShortName":"Checkmk","dateReserved":"2026-08-20T08:31:22.429Z","datePublished":"2026-09-21T10:57:37.433Z","dateUpdated":"2026-09-21T19:40:26.202Z"},"containers":{"cna":{"affected":[{"defaultStatus":"unaffected","product":"Checkmk","vendor":"Checkmk GmbH","versions":[{"lessThan":"2.5.0p14","status":"affected","version":"2.5.0","versionType":"semver"},{"lessThan":"2.4.0p37","status":"affected","version":"2.4.0","versionType":"semver"},{"lessThan":"2.3.0p51","status":"affected","version":"2.3.0","versionType":"semver"},{"status":"affected","version":"2.2.0","versionType":"semver"}]}],"credits":[{"lang":"en","type":"reporter","value":"Sven Jäger (SySS GmbH)"}],"descriptions":[{"lang":"en","value":"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."}],"impacts":[{"capecId":"CAPEC-197","descriptions":[{"lang":"en","value":"CAPEC-197: Exponential Data Expansion"}]}],"metrics":[{"cvssV4_0":{"baseScore":5.3,"baseSeverity":"MEDIUM","vectorString":"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","version":"4.0"}}],"problemTypes":[{"descriptions":[{"cweId":"CWE-409","description":"CWE-409: Improper Handling of Highly Compressed Data (Data Amplification)","lang":"en","type":"CWE"}]}],"providerMetadata":{"orgId":"f7d6281c-4801-44ce-ace2-493291dedb0f","shortName":"Checkmk","dateUpdated":"2026-09-21T10:57:37.433Z"},"references":[{"url":"https://checkmk.com/werk/22116","tags":["vendor-advisory"]}],"title":"Missing decompression size limit in agent receiver allows memory exhaustion via push agent data","cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:a:checkmk:checkmk:*:*:*:*:*:*:*:*","versionStartIncluding":"2.5.0","versionEndExcluding":"2.5.0p14"},{"vulnerable":true,"criteria":"cpe:2.3:a:checkmk:checkmk:*:*:*:*:*:*:*:*","versionStartIncluding":"2.4.0","versionEndExcluding":"2.4.0p37"},{"vulnerable":true,"criteria":"cpe:2.3:a:checkmk:checkmk:*:*:*:*:*:*:*:*","versionStartIncluding":"2.3.0","versionEndExcluding":"2.3.0p51"},{"vulnerable":true,"criteria":"cpe:2.3:a:checkmk:checkmk:2.2.0:*:*:*:*:*:*:*"}]}]}]},"adp":[{"metrics":[{"other":{"type":"ssvc","content":{"id":"CVE-2026-77021","role":"CISA Coordinator","options":[{"Exploitation":"none"},{"Automatable":"no"},{"Technical Impact":"partial"}],"version":"2.0.3","timestamp":"2026-09-21T14:40:45.554408Z"}}}],"title":"CISA ADP Vulnrichment","providerMetadata":{"orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","shortName":"CISA-ADP","dateUpdated":"2026-09-21T19:40:26.202Z"}}]}}