Security advisory

{
  "id": "dc015ef478bf174ace0534fac02274226128251f81a74907b97b1b5952cdeefd",
  "url": "https://osv.dev/vulnerability/CVE-2021-25833",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "CVE-2021-25833",
    "summary": "A file extension handling issue was found in [server] module of ONLYOFFICE DocumentServer v4.2.0.71-v5.6.0.21. The file extension is controlled by an attacker through the request data and leads to arbitrary file overwriting. Using this vulnerability, a remote attacker can obtain remote code execution on DocumentServer.",
    "evidence": "osv:CVE-2021-25833",
    "products": [],
    "severity": "critical",
    "structured": {
      "id": "CVE-2021-25833",
      "aliases": [
        "CVE-2021-25833"
      ],
      "metrics": [
        {
          "type": "CVSS_V3",
          "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://github.com/onlyoffice/server",
              "type": "GIT",
              "events": [
                {
                  "introduced": "761b989ff2a0b022ea2526bbd798d285150c3c54"
                },
                {
                  "last_affected": "ec87c3fd5e9ed78e1711d473c9f7052883fd6f5b"
                }
              ],
              "database_specific": {
                "extracted_events": [
                  {
                    "cpe": "cpe:2.3:a:onlyoffice:document_server:*:*:*:*:*:*:*:*",
                    "range": [
                      {
                        "introduced": "4.2.0.71"
                      },
                      {
                        "last_affected": "5.6.0.21"
                      }
                    ],
                    "source": "CPE_RANGE"
                  }
                ]
              }
            }
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2021-25833.json"
          }
        }
      ],
      "modified": "2026-10-24T02:46:41.138742158Z",
      "provider": "osv",
      "references": [
        "https://github.com/ONLYOFFICE/server/blob/v5.6.0.21/DocService/sources/converterservice.js#L200",
        "https://github.com/ONLYOFFICE/server/blob/v5.6.0.21/FileConverter/sources/converter.js#L283",
        "https://github.com/ONLYOFFICE/server/blob/v5.6.0.21/FileConverter/sources/converter.js#L593",
        "https://github.com/ONLYOFFICE/DocumentServer",
        "https://github.com/ONLYOFFICE/server",
        "https://github.com/merrychap/poc_exploits/tree/master/ONLYOFFICE/CVE-2021-25833"
      ],
      "provider_metadata": {}
    },
    "related_cves": [
      {
        "value": "CVE-2021-25833",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 428165,
  "published_at": "2021-03-01T16:15:14.51+00:00"
}