{"id":"CVE-2021-25831","aliases":["EUVD-2021-12714","GHSA-m252-hx7q-7p3h"],"status":"published","title":"A file extension handling issue was found in [core] module of ONLYOFFICE DocumentServer v4.0.0-9...","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.","severity":{"version":"3.1","score":9.8,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","level":"critical","assessor":"primary","from":"nvd"},"epss":{"day":"2026-11-10","score":0.11503,"percentile":0.96055,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":false},"published":"2021-03-01T15:08:37Z","modified":"2026-10-20T10:54:33Z","products":[{"vendor":"onlyoffice","product":"document_server"}],"references":[{"url":"https://github.com/ONLYOFFICE/DocumentServer","tags":["x_refsource_MISC","x_transferred","Product","package"]},{"url":"https://github.com/ONLYOFFICE/core","tags":["x_refsource_MISC","x_transferred","Product","Vendor Advisory","package"]},{"url":"https://github.com/ONLYOFFICE/core/blob/v5.6.4.13/ASCOfficePPTXFile/Editor/BinaryFileReaderWriter.cpp#L241","tags":["x_refsource_MISC","x_transferred","Vendor Advisory","advisory"]},{"url":"https://github.com/ONLYOFFICE/core/blob/v5.6.4.13/ASCOfficePPTXFile/Editor/BinaryFileReaderWriter.cpp#L1918","tags":["x_refsource_MISC","x_transferred","Vendor Advisory","advisory"]},{"url":"https://github.com/ONLYOFFICE/core/blob/v5.6.4.13/ASCOfficePPTXFile/PPTXFormat/Logic/Fills/BlipFill.cpp#L328","tags":["x_refsource_MISC","x_transferred","Vendor Advisory","advisory"]},{"url":"https://github.com/merrychap/poc_exploits/tree/master/ONLYOFFICE/CVE-2021-25831","tags":["x_refsource_MISC","x_transferred","Exploit","Vendor Advisory","evidence"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2021-25831"},{"url":"https://github.com/advisories/GHSA-m252-hx7q-7p3h"}],"sources":{"cve":[{"id":"CVE-2021-25831","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.","status":"published","published":"2021-03-01T15:08:37Z","modified":"2024-08-03T20:11:28.475Z","updated_at":"2026-11-02T14:32:59.802172Z"}],"euvd":[{"id":"EUVD-2021-12714","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.","status":"published","published":"2021-03-01T15:08:37Z","modified":"2024-08-03T20:11:28Z","updated_at":"2026-11-03T03:24:52.420769Z"}],"ghsa":[{"id":"GHSA-m252-hx7q-7p3h","title":"A file extension handling issue was found in [core] module of ONLYOFFICE DocumentServer v4.0.0-9...","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.","status":"published","published":"2022-05-24T17:43:24Z","modified":"2023-01-29T05:05:54Z","updated_at":"2026-11-02T14:45:54.221809Z"}],"nvd":[{"id":"CVE-2021-25831","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.","status":"published","published":"2021-03-01T16:15:14.353Z","modified":"2026-06-17T03:42:29.403Z","cvss":[{"version":"3.1","score":9.8,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","level":"critical","assessor":"primary"},{"version":"2.0","score":7.5,"vector":"AV:N/AC:L/Au:N/C:P/I:P/A:P","level":"high","assessor":"primary"}],"updated_at":"2026-11-02T14:06:50.399901Z"}],"osv":[{"id":"CVE-2021-25831","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.","status":"published","published":"2021-03-01T16:15:14.353Z","modified":"2026-10-20T10:54:33.438234141Z","cvss":[{"version":"3.1","score":9.8,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","level":"critical"}],"updated_at":"2026-11-02T15:44:18.778776Z"}]}}