{"id":"CVE-2026-77021","state":"PUBLISHED","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.","publishedAt":"2026-09-21T10:57:37.433Z","updatedAt":"2026-09-21T19:40:26.202Z","severity":{"score":5.3,"label":"Medium","version":"4.0","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","source":"Checkmk"},"assigner":"Checkmk","products":["Checkmk GmbH Checkmk"],"affected":[{"vendor":"Checkmk GmbH","product":"Checkmk","defaultStatus":"unaffected","versions":[{"version":"2.5.0","status":"affected","lessThan":"2.5.0p14","versionType":"semver"},{"version":"2.4.0","status":"affected","lessThan":"2.4.0p37","versionType":"semver"},{"version":"2.3.0","status":"affected","lessThan":"2.3.0p51","versionType":"semver"},{"version":"2.2.0","status":"affected","versionType":"semver"}]}],"references":["https://checkmk.com/werk/22116"],"weaknesses":["CWE-409"],"ingestedAt":"2026-10-29T20:13:07.220Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/77xxx/CVE-2026-77021.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-77021","state":"PUBLISHED","datePublished":"2026-09-21T10:57:37.433Z","dateUpdated":"2026-09-21T19:40:26.202Z","assignerShortName":"Checkmk","assignerOrgId":"f7d6281c-4801-44ce-ace2-493291dedb0f","dateReserved":"2026-08-20T08:31:22.429Z"},"containers":{"cna":{"title":"Missing decompression size limit in agent receiver allows memory exhaustion via push agent data","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."}],"affected":[{"vendor":"Checkmk GmbH","product":"Checkmk","defaultStatus":"unaffected","versions":[{"version":"2.5.0","status":"affected","lessThan":"2.5.0p14","versionType":"semver"},{"version":"2.4.0","status":"affected","lessThan":"2.4.0p37","versionType":"semver"},{"version":"2.3.0","status":"affected","lessThan":"2.3.0p51","versionType":"semver"},{"version":"2.2.0","status":"affected","versionType":"semver"}]}],"references":[{"url":"https://checkmk.com/werk/22116","tags":["vendor-advisory"]}],"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":{"shortName":"Checkmk","orgId":"f7d6281c-4801-44ce-ace2-493291dedb0f","dateUpdated":"2026-09-21T10:57:37.433Z"},"credits":[{"lang":"en","type":"reporter","value":"Sven Jäger (SySS GmbH)"}],"impacts":[{"capecId":"CAPEC-197","descriptions":[{"lang":"en","value":"CAPEC-197: Exponential Data Expansion"}]}],"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":[{"title":"CISA ADP Vulnrichment","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"}}}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-09-21T19:40:26.202Z"}}]}}}