What’s Vulnerable › Vulnerabilities

CVE-2021-3199: ONLYOFFICE Docs Server Path Traversal Vulnerability

• Severity: critical (CVSS 9.8 v3.1)
• Exploited in the wild: yes — in CISA KEV since 2026-10-08
• EPSS: 30.2% probability of exploitation in the next 30 days
• Public exploit or detection template: yes
• Published: 2021-01-26 · updated 2026-10-09
• Weakness: CWE-22

Description

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.

Affected products

• ONLYOFFICE Document Server: before 5.6.3 — fixed in 5.6.3

How to fix

Upgrade to a fixed version: ONLYOFFICE Document Server 5.6.3. Check the vendor advisory for mitigations.

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://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://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-3199

Get alerted when CVE-2021-3199 or the next vulnerability affects your stack