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.

Score

CVSS 3.1 9.8 Critical

Status

Analyzed - cve@mitre.org

Published

2021-01-26

Last modified

2026-10-09

Known exploited (CISA KEV)

since 2026-10-08, action due 2026-10-11: 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.

Weaknesses

CWE-22

Affected products

• Document Server (Onlyoffice)

References

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