CVE-2021-25830 in the critical feed json
A file extension handling issue was found in [core] module of ONLYOFFICE DocumentServer v4.2.0.236-v5.6.4.13.
published 2021-03-01 5 y ago modified 2026-06-17 4 mo ago also EUVD-2021-12713
- cvss
- 9.8
- version 3.1, NVD
- cisa kev
- Not listed
- not in CISA's catalog
- epss
- 11.8%
- EPSS 11.8% chance of exploitation in 30 days, percentile 96%
- public exploits
- 0
- none known
Summary
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.
Exploit prediction
11.76% chance of exploitation in the next 30 days, higher than 96% of all scored CVEs (FIRST EPSS, 2026-11-08).
Exploits and checks
- github.com https://github.com/merrychap/poc_exploits/tree/master/ONLYOFFICE/CVE-2021-25830 referenced PoC, tagged "exploit" by a source, unverified
CVSS scores
| assigned by | version | score | vector |
|---|---|---|---|
| NVD | 3.1 | 9.8 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H |
| NVD | 2.0 | 7.5 | AV:N/AC:L/Au:N/C:P/I:P/A:P |
References
-
github.com
/merrychap/poc_exploits/tree/master/ONLYOFFICE/CVE-2021-25830
exploit, third-party-advisory
-
github.com
/ONLYOFFICE/DocumentServer
product
-
github.com
/ONLYOFFICE/core
product
-
github.com
/ONLYOFFICE/core/blob/v5.6.4.13/ASCOfficePPTXFile/PPTXFormat/Logic/UniFill.cpp#L343
third-party-advisory
-
github.com
/ONLYOFFICE/core/blob/v5.6.4.13/ASCOfficePPTXFile/Editor/BinaryFileReaderWriter.cpp#L241
third-party-advisory
-
github.com
/ONLYOFFICE/core/blob/v5.6.4.13/ASCOfficePPTXFile/Editor/BinaryFileReaderWriter.cpp#L1918
third-party-advisory
Sources
- CVE List CVE-2021-25830
- NVD CVE-2021-25830
Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.