What is CVE-2021-3199?
Directory traversal with remote code execution can occur in /upload in ONLYOFFICE Document Server before 5.6.3, when JWT is used, via a /.. sequence in an image upload parameter.
Timeline
- 2021-01-26Published to the U.S. National Vulnerability Database (NVD)
- 2026-10-08Added to the CISA Known Exploited Vulnerabilities (KEV) catalog
- 2026-10-09NVD record last updated
- 2026-10-11CISA federal remediation deadline (BOD 22-01)
CISA Known Exploited Vulnerability
ONLYOFFICE Docs Server Path Traversal Vulnerability
Affected product
ONLYOFFICE Docs
Remediation Steps
- Apply the vendor security update for ONLYOFFICE Docs as a priority.
- Restrict network exposure of the affected service to trusted sources until patched.
- Review logs and detections for indicators of exploitation.
- Confirm fixed versions against the official vendor advisory before deploying.
References
- https://github.com/ONLYOFFICE/DocumentServer/blob/903fe5ab7a275bd69c3c3346af2d21cf87ebeabf/CHANGELOG.md#563
- https://github.com/moehw/poc_exploits/tree/master/CVE-2021-3199/poc_uploadImageFile.py
- https://github.com/nola-milkin/poc_exploits/blob/master/CVE-2021-3199/poc_uploadImageFile.py
- https://nvd.nist.gov/vuln/detail/CVE-2021-3199
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog
Referenced in our briefings & reports
- Vulnerability Priority Report – Week 1 of October 2026 (October 5 – 11)
Browse all tracked CVEs in the defend.network CVE database →
🤖 This CVE page is generated by defend.network from NVD, CISA KEV, EPSS, and our verified daily briefings. Severity and exploitation data come from official sources; always verify remediation steps against the official vendor advisory before acting in production.