{"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 J\u00e4ger (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"}}]}}