CVE-2021-25830
An attacker must request the conversion of the crafted file from DOCT into DOCX format.
Does this matter?
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.
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.
- CVSS 3.1
- 9.8 CRITICALCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- EPSS
- 11.76% probability · 96th percentile
- Public exploits
- None in Exploit-DB
- CISA KEV
- Not listed
- Affected
- onlyoffice/document server
- Source
- cve@mitre.org
EPSS 11.8% since 3 November 2026; no change recorded yet. The dashed line is the ten per cent mark our analysts treat as “patch before the next change window”. Points are recorded when the score first appears and whenever it moves by a percentage point or more.
References
- https://github.com/ONLYOFFICE/DocumentServerProduct
- https://github.com/ONLYOFFICE/coreProduct
- https://github.com/ONLYOFFICE/core/blob/v5.6.4.13/ASCOfficePPTXFile/Editor/BinaryFileReaderWriter.cpp#L1918Third Party Advisory
- https://github.com/ONLYOFFICE/core/blob/v5.6.4.13/ASCOfficePPTXFile/Editor/BinaryFileReaderWriter.cpp#L241Third Party Advisory
- https://github.com/ONLYOFFICE/core/blob/v5.6.4.13/ASCOfficePPTXFile/PPTXFormat/Logic/UniFill.cpp#L343Third Party Advisory
- https://github.com/merrychap/poc_exploits/tree/master/ONLYOFFICE/CVE-2021-25830Exploit, Third Party Advisory
- https://github.com/ONLYOFFICE/DocumentServerProduct
- https://github.com/ONLYOFFICE/coreProduct
- https://github.com/ONLYOFFICE/core/blob/v5.6.4.13/ASCOfficePPTXFile/Editor/BinaryFileReaderWriter.cpp#L1918Third Party Advisory
- https://github.com/ONLYOFFICE/core/blob/v5.6.4.13/ASCOfficePPTXFile/Editor/BinaryFileReaderWriter.cpp#L241Third Party Advisory
- https://github.com/ONLYOFFICE/core/blob/v5.6.4.13/ASCOfficePPTXFile/PPTXFormat/Logic/UniFill.cpp#L343Third Party Advisory
- https://github.com/merrychap/poc_exploits/tree/master/ONLYOFFICE/CVE-2021-25830Exploit, Third Party Advisory
Source: NVD record, EPSS from FIRST.org, KEV from CISA, exploits from Exploit-DB. Refreshed daily. Download this record as JSON.