{"id":"CVE-2021-25830","url":"https://www.cyber-defence.io/tools/cve/CVE-2021-25830","generatedAt":"2026-11-05T01:39:14.506Z","title":"An attacker must request the conversion of the crafted file from DOCT into DOCX format.","description":"A file extension handling issue was found in [core] module of ONLYOFFICE DocumentServer v4.2.0.236-v5.6.4.13. An attacker must request the conversion of the crafted file from DOCT into DOCX format. Using the chain of two other bugs related to improper string handling, an attacker can achieve remote code execution on DocumentServer.","published":"2021-03-01T16:15:14.000Z","lastModified":"2026-06-17T03:42:29.000Z","status":"Modified","sourceIdentifier":"cve@mitre.org","cvss":{"version":"3.1","score":9.8,"severity":"CRITICAL","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H"},"cwe":[],"affected":["onlyoffice/document server"],"epss":{"score":0.11763,"percentile":0.9608,"date":"2026-11-03","history":[]},"kev":{"listed":false},"exploits":{"count":0,"verified":false,"firstPublished":null,"source":"Exploit-DB (https://gitlab.com/exploit-database/exploitdb)","entries":[]},"verdict":{"level":"urgent","text":"EPSS puts the probability of exploitation in the next 30 days at 11.8%, higher than 96% of all known CVEs. Patch or mitigate before the next change window."},"changes":[],"references":[{"url":"https://github.com/ONLYOFFICE/DocumentServer","tags":["Product"],"source":"cve@mitre.org"},{"url":"https://github.com/ONLYOFFICE/core","tags":["Product"],"source":"cve@mitre.org"},{"url":"https://github.com/ONLYOFFICE/core/blob/v5.6.4.13/ASCOfficePPTXFile/Editor/BinaryFileReaderWriter.cpp#L1918","tags":["Third Party Advisory"],"source":"cve@mitre.org"},{"url":"https://github.com/ONLYOFFICE/core/blob/v5.6.4.13/ASCOfficePPTXFile/Editor/BinaryFileReaderWriter.cpp#L241","tags":["Third Party Advisory"],"source":"cve@mitre.org"},{"url":"https://github.com/ONLYOFFICE/core/blob/v5.6.4.13/ASCOfficePPTXFile/PPTXFormat/Logic/UniFill.cpp#L343","tags":["Third Party Advisory"],"source":"cve@mitre.org"},{"url":"https://github.com/merrychap/poc_exploits/tree/master/ONLYOFFICE/CVE-2021-25830","tags":["Exploit","Third Party Advisory"],"source":"cve@mitre.org"},{"url":"https://github.com/ONLYOFFICE/DocumentServer","tags":["Product"],"source":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://github.com/ONLYOFFICE/core","tags":["Product"],"source":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://github.com/ONLYOFFICE/core/blob/v5.6.4.13/ASCOfficePPTXFile/Editor/BinaryFileReaderWriter.cpp#L1918","tags":["Third Party Advisory"],"source":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://github.com/ONLYOFFICE/core/blob/v5.6.4.13/ASCOfficePPTXFile/Editor/BinaryFileReaderWriter.cpp#L241","tags":["Third Party Advisory"],"source":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://github.com/ONLYOFFICE/core/blob/v5.6.4.13/ASCOfficePPTXFile/PPTXFormat/Logic/UniFill.cpp#L343","tags":["Third Party Advisory"],"source":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://github.com/merrychap/poc_exploits/tree/master/ONLYOFFICE/CVE-2021-25830","tags":["Exploit","Third Party Advisory"],"source":"af854a3a-2127-422b-91ae-364da2661108"}],"sources":{"nvd":"https://nvd.nist.gov/vuln/detail/CVE-2021-25830","epss":"https://www.first.org/epss/","kev":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog","exploitdb":"https://www.exploit-db.com/"},"licence":"CC BY 4.0 — link back to the CVE Explorer if you publish the results; upstream data remains subject to its own terms."}