CVE-2021-3199

CRITICAL

9.8

CVSS Score

Published: January 22, 2021 at 02:41 AM UTC

Updated: October 9, 2026 at 02:20 PM UTC

2 products affected across 2 vendorsDocument ServerONLYOFFICE Document Server

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Severity

CRITICAL9.8

Exploitation

CISA KEV

Exploit prediction

EPSS 30%

SSVC

Active

Actively Exploited

CISA Known Exploited Vulnerabilities (KEV) Catalog

EPSS Score30.2%

EPSS (Exploit Prediction Scoring System) estimates a 30.2% chance this CVE is exploited in the wild within the next 30 days — higher than 98% of all CVEs. It complements CVSS: a high EPSS on a mid-severity CVE can still be urgent.

ONLYOFFICE Docs contains a path traversal vulnerability that can occur when JWT is used, via a /.. sequence in an image upload parameter and could allow for remote code execution.

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.

Ransomware Use

Unknown

Added to KEV

Oct 8, 2026

Remediation Due

Oct 11, 2026

17 days overdue

Notes

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/CVE-2021-3199

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.