CVE-2021-3199

Critical

ONLYOFFICE Docs Server Path Traversal Vulnerability

9.8 CVSS v3.1

Published: Jan 26, 2021
Updated: Oct 9, 2026
Vendor: Onlyoffice
Affected versions: See affected products
Weakness: CWE-22

Summary

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.

Severity

Critical (9.8)

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Affected products

Onlyoffice Document Server < 5.6.3

Exploitation status

Actively exploited

Listed in the CISA Known Exploited Vulnerabilities catalog on Oct 8, 2026. Federal remediation due: Oct 11, 2026.

Technical details

Technical analysis has not been written for this record yet.

Mitigation & remediation

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.