{
    "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"
                }
            }
        ]
    }
}