{
    "id": "CVE-2021-25831",
    "published": "2021-03-01 16:15:14",
    "last_modified": "2026-06-17 03:42:29",
    "cvss_score": "9.8",
    "cvss_severity": "CRITICAL",
    "cvss_version": "3.1",
    "cvss_vector": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
    "cwe": null,
    "description": "A file extension handling issue was found in [core] module of ONLYOFFICE DocumentServer v4.0.0-9-v5.6.3. An attacker must request the conversion of the crafted file from PPTT into PPTX format. Using the chain of two other bugs related to improper string handling, a remote attacker can obtain remote code execution on DocumentServer.",
    "epss_score": "0.11503",
    "epss_percentile": "0.95907",
    "kev": 0,
    "kev_due": null,
    "has_exploit": 0,
    "updated_at": "2026-10-03 18:17:28",
    "priority": {
        "rank": 2,
        "label": "Patch early",
        "why": "EPSS 11.5% — above the 10% action threshold."
    },
    "products": [
        {
            "vendor": "onlyoffice",
            "product": "document_server"
        }
    ],
    "kev_detail": null,
    "exploits": [],
    "refs_list": [
        "https://github.com/ONLYOFFICE/DocumentServer",
        "https://github.com/ONLYOFFICE/core",
        "https://github.com/ONLYOFFICE/core/blob/v5.6.4.13/ASCOfficePPTXFile/Editor/BinaryFileReaderWriter.cpp#L1918",
        "https://github.com/ONLYOFFICE/core/blob/v5.6.4.13/ASCOfficePPTXFile/Editor/BinaryFileReaderWriter.cpp#L241",
        "https://github.com/ONLYOFFICE/core/blob/v5.6.4.13/ASCOfficePPTXFile/PPTXFormat/Logic/Fills/BlipFill.cpp#L328",
        "https://github.com/merrychap/poc_exploits/tree/master/ONLYOFFICE/CVE-2021-25831",
        "https://github.com/ONLYOFFICE/DocumentServer",
        "https://github.com/ONLYOFFICE/core",
        "https://github.com/ONLYOFFICE/core/blob/v5.6.4.13/ASCOfficePPTXFile/Editor/BinaryFileReaderWriter.cpp#L1918",
        "https://github.com/ONLYOFFICE/core/blob/v5.6.4.13/ASCOfficePPTXFile/Editor/BinaryFileReaderWriter.cpp#L241",
        "https://github.com/ONLYOFFICE/core/blob/v5.6.4.13/ASCOfficePPTXFile/PPTXFormat/Logic/Fills/BlipFill.cpp#L328",
        "https://github.com/merrychap/poc_exploits/tree/master/ONLYOFFICE/CVE-2021-25831"
    ]
}