CVE-2021-3199: ONLYOFFICE Document Server /upload path traversal to RCE
Exploited in the wild Critical 9.8 EPSS 30.2%
ONLYOFFICE Document Server before 5.6.3, when JWT is used, has a directory traversal in /upload through a /.. sequence in an image-upload parameter, which can lead to remote code execution; public proof-of-concept code exists. It was fixed in Document Server 5.6.3 ('Fix Path Traversal vulnerability via image upload params', bug #46113). CISA added it to the Known Exploited Vulnerabilities catalog on 2026-10-08.
- CVE-2021-3199CVE identifier
- 9.8CVSS 3.1 base score (critical)
- 2026-10-08added to CISA's exploited list (US federal deadline 2026-10-11)
- 30.2%EPSS: chance of exploitation in the next 30 days (higher than 98% of CVEs)
- 2021-01-22published
What do these terms mean? CVE · CVSS score · exploited (KEV) · EPSS · backported fix · all terms
What to do now
- Check whether you run the affected software and which version (commands below).
- Install the fixed version for your system: see “Patch it” below.
- Restart the affected service (or reboot for kernel and library updates) so the fix is actually in use.
- Because this flaw is being exploited, also check the server for signs of compromise.
Affected and fixed versions
Affected:
- ONLYOFFICE Document Server before 5.6.3
Fixed in:
- ONLYOFFICE Document Server 5.6.3
Patch it
Use the commands for your system. Distribution packages often keep an older version number with the fix backported, so compare with the fixed package versions in the table below, not only with the upstream version.
Docker images
docker pull onlyoffice/documentserver:latest # 5.6.3 or later; tag 5.6.3 exists
# recreate the container from the new imageGeneral update steps for every system are on the Linux and Unix & BSD pages; after updating, see which services to restart.
CISA required action: Apply mitigations in accordance with vendor instructions, ensuring compliance with CISA’s BOD 26-04 Prioritizing Security Updates Based on Risk (see URL in Notes) guidance and CISA’s “Forensics Triage Requirements” (see URL in Notes). Follow applicable BOD 26-04 guidance for cloud services or discontinue use of the product if mitigations are unavailable. Stakeholders are responsible for evaluating each asset's internet exposure and ensuring adherence to BOD 26-04 patching guidelines.
This vulnerability could affect an open-source component, third-party library, protocol, or proprietary implementation that could be used by different products. For more information, please see: ; https://github.com/ONLYOFFICE/DocumentServer/blob/903fe5ab7a275bd69c3c3346af2d21cf87ebeabf/CHANGELOG.md#563 ; BOD 26-04: https://www.cisa.gov/news-events/directives/bod-26-04-prioritizing-security-updates-based-risk ; Forensics Triage Requirements: https://www.cisa.gov/news-events/directives/bod-26-04-implementation-guidance-prioritizing-security-updates-based-risk ; https://nvd.nist.gov/vuln/detail/
Sources
- ONLYOFFICE DocumentServer CHANGELOG (5.6.3)
- Docker Hub onlyoffice/documentserver
- CVE record CVE-2021-3199
- https://github.com/ONLYOFFICE/DocumentServer/blob/903fe5ab7a275bd69c3c3346af2d21cf87ebeabf/CHANGELOG.md#563
- https://github.com/nola-milkin/poc_exploits/blob/master/CVE-2021-3199/poc_uploadImageFile.py
- https://github.com/moehw/poc_exploits/tree/master/CVE-2021-3199/poc_uploadImageFile.py
- CVE-2021-3199 on CVE.org
- CVE-2021-3199 on NVD
- CISA Known Exploited Vulnerabilities catalog
Page generated automatically from official sources on 2026-11-03 18:05 UTC and reviewed by an editor. Always confirm with your vendor's advisory.