CVE-2021-25830
9.8
CRITICAL · CVSS 3.1 · EPSS 11.8% (pctl 96)
Patch early
EPSS 11.8% — above the 10% action threshold.
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.
Scoring
| CVSS | 9.8 (CRITICAL, v3.1) |
|---|---|
| Vector | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H |
| EPSS | 11.76% — more likely to be exploited than 96% of all CVEs |
| On CISA KEV | no |
| Public exploit | none known |
| Published | 2021-03-01 |
| Last modified | 2026-06-17 |
Affected (1)
| Vendor | Product |
|---|---|
| onlyoffice | document server |
References
- https://github.com/ONLYOFFICE/DocumentServer
- https://github.com/ONLYOFFICE/core
- https://github.com/ONLYOFFICE/core/blob/v5.6.4.13/ASCOfficePPTXFile/Editor/BinaryFileReaderWriter.cpp#L1918
- https://github.com/ONLYOFFICE/core/blob/v5.6.4.13/ASCOfficePPTXFile/Editor/BinaryFileReaderWriter.cpp#L241
- https://github.com/ONLYOFFICE/core/blob/v5.6.4.13/ASCOfficePPTXFile/PPTXFormat/Logic/UniFill.cpp#L343
- https://github.com/merrychap/poc_exploits/tree/master/ONLYOFFICE/CVE-2021-25830
- https://github.com/ONLYOFFICE/DocumentServer
- https://github.com/ONLYOFFICE/core
- https://github.com/ONLYOFFICE/core/blob/v5.6.4.13/ASCOfficePPTXFile/Editor/BinaryFileReaderWriter.cpp#L1918
- https://github.com/ONLYOFFICE/core/blob/v5.6.4.13/ASCOfficePPTXFile/Editor/BinaryFileReaderWriter.cpp#L241
- https://github.com/ONLYOFFICE/core/blob/v5.6.4.13/ASCOfficePPTXFile/PPTXFormat/Logic/UniFill.cpp#L343
- https://github.com/merrychap/poc_exploits/tree/master/ONLYOFFICE/CVE-2021-25830
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