CVE-2021-25833
The file extension is controlled by an attacker through the request data and leads to arbitrary file overwriting.
Does this matter?
EPSS puts the probability of exploitation in the next 30 days at 43.5%, higher than 99% of all known CVEs. Patch or mitigate before the next change window.
Description
A file extension handling issue was found in [server] module of ONLYOFFICE DocumentServer v4.2.0.71-v5.6.0.21. The file extension is controlled by an attacker through the request data and leads to arbitrary file overwriting. Using this vulnerability, a remote attacker can obtain 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
- 43.53% probability · 99th percentile
- Public exploits
- None in Exploit-DB
- CISA KEV
- Not listed
- Weakness
- CWE-22
- Affected
- onlyoffice/document server
- Source
- cve@mitre.org
EPSS 43.5% 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, Vendor Advisory
- https://github.com/ONLYOFFICE/serverProduct
- https://github.com/ONLYOFFICE/server/blob/v5.6.0.21/DocService/sources/converterservice.js#L200Third Party Advisory
- https://github.com/ONLYOFFICE/server/blob/v5.6.0.21/FileConverter/sources/converter.js#L283Third Party Advisory
- https://github.com/ONLYOFFICE/server/blob/v5.6.0.21/FileConverter/sources/converter.js#L593Third Party Advisory
- https://github.com/merrychap/poc_exploits/tree/master/ONLYOFFICE/CVE-2021-25833Exploit, Third Party Advisory
- https://github.com/ONLYOFFICE/DocumentServerProduct, Vendor Advisory
- https://github.com/ONLYOFFICE/serverProduct
- https://github.com/ONLYOFFICE/server/blob/v5.6.0.21/DocService/sources/converterservice.js#L200Third Party Advisory
- https://github.com/ONLYOFFICE/server/blob/v5.6.0.21/FileConverter/sources/converter.js#L283Third Party Advisory
- https://github.com/ONLYOFFICE/server/blob/v5.6.0.21/FileConverter/sources/converter.js#L593Third Party Advisory
- https://github.com/merrychap/poc_exploits/tree/master/ONLYOFFICE/CVE-2021-25833Exploit, Third Party Advisory
Source: NVD record, EPSS from FIRST.org, KEV from CISA, exploits from Exploit-DB. Refreshed daily. Download this record as JSON.