{"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": "2026-09-21T10:57:37.433Z"}, "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:*:*:*:*:*:*:*"}]}]}]}}}

{}

{"affected": [{"affectedData": [{"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"}]}], "source": "security@checkmk.com"}], "cveTags": [], "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."}], "id": "CVE-2026-77021", "lastModified": "2026-09-21T11:17:12.360", "metrics": {"cvssMetricV40": [{"cvssData": {"Automatable": "NOT_DEFINED", "Recovery": "NOT_DEFINED", "Safety": "NOT_DEFINED", "attackComplexity": "LOW", "attackRequirements": "NONE", "attackVector": "NETWORK", "availabilityRequirement": "NOT_DEFINED", "baseScore": 5.3, "baseSeverity": "MEDIUM", "confidentialityRequirement": "NOT_DEFINED", "exploitMaturity": "NOT_DEFINED", "integrityRequirement": "NOT_DEFINED", "modifiedAttackComplexity": "NOT_DEFINED", "modifiedAttackRequirements": "NOT_DEFINED", "modifiedAttackVector": "NOT_DEFINED", "modifiedPrivilegesRequired": "NOT_DEFINED", "modifiedSubAvailabilityImpact": "NOT_DEFINED", "modifiedSubConfidentialityImpact": "NOT_DEFINED", "modifiedSubIntegrityImpact": "NOT_DEFINED", "modifiedUserInteraction": "NOT_DEFINED", "modifiedVulnAvailabilityImpact": "NOT_DEFINED", "modifiedVulnConfidentialityImpact": "NOT_DEFINED", "modifiedVulnIntegrityImpact": "NOT_DEFINED", "privilegesRequired": "LOW", "providerUrgency": "NOT_DEFINED", "subAvailabilityImpact": "NONE", "subConfidentialityImpact": "NONE", "subIntegrityImpact": "NONE", "userInteraction": "NONE", "valueDensity": "NOT_DEFINED", "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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X", "version": "4.0", "vulnAvailabilityImpact": "LOW", "vulnConfidentialityImpact": "NONE", "vulnIntegrityImpact": "NONE", "vulnerabilityResponseEffort": "NOT_DEFINED"}, "source": "security@checkmk.com", "type": "Secondary"}]}, "published": "2026-09-21T11:17:12.200", "references": [{"source": "security@checkmk.com", "url": "https://checkmk.com/werk/22116"}], "sourceIdentifier": "security@checkmk.com", "vulnStatus": "Deferred", "weaknesses": [{"description": [{"lang": "en", "value": "CWE-409"}], "source": "security@checkmk.com", "type": "Secondary"}]}

{}

{"affected": [{"configurations": [{"platform": null, "status": "affected", "versions": {"scheme": "generic", "value": "[2.5.0,2.5.0p14)"}}, {"platform": null, "status": "affected", "versions": {"scheme": "generic", "value": "[2.4.0,2.4.0p37)"}}, {"platform": null, "status": "affected", "versions": {"scheme": "generic", "value": "[2.3.0,2.3.0p51)"}}, {"platform": null, "status": "affected", "versions": {"scheme": "semver", "value": "2.2.0"}}], "enrichment": {"confidence": 95.0, "confidence_source": "inferred", "scores": [{"score": 95.0, "source": "inferred"}, {"score": 100.0, "source": "matching"}]}, "original": {"product": "Checkmk", "source": "cna", "vendor": "Checkmk GmbH"}, "product": "checkmk", "vendor": "checkmk"}], "created": "2026-09-21T12:30:14.781186+00:00", "updated": "2026-09-21T13:15:08.926305+00:00", "vendors": ["checkmk", "checkmk$PRODUCT$checkmk"]}