CVE-2021-3199: ONLYOFFICE Docs Server Path Traversal Vulnerability
Affects ONLYOFFICE DocsSource CISA KEV
No CVSS score published yet
- Exploitation
Actively exploited – in CISA KEV since 10/08/2026
- KEV deadline
- 10/11/2026
- EPSS
- 20.1% chance of exploitation in 30 days – higher than 97% of CVEs
What to do
CISA 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.
- github.com/ONLYOFFICE/DocumentServer/blob/903fe5ab7a275bd69c3c3346af2d21cf87ebeabf/CHANGELOG.md (opens in a new tab)
- cisa.gov/news-events/directives/bod-26-04-prioritizing-security-updates-based-risk (opens in a new tab)
- cisa.gov/news-events/directives/bod-26-04-implementation-guidance-prioritizing-security-updates-based-risk (opens in a new tab)
- nvd.nist.gov/vuln/detail/CVE-2021-3199 (opens in a new tab)
Description
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.
Weaknesses
References
- github.com/ONLYOFFICE/DocumentServer/blob/903fe5ab7a275bd69c3c3346af2d21cf87ebeabf/CHANGELOG.md (opens in a new tab)
- cisa.gov/news-events/directives/bod-26-04-prioritizing-security-updates-based-risk (opens in a new tab)
- cisa.gov/news-events/directives/bod-26-04-implementation-guidance-prioritizing-security-updates-based-risk (opens in a new tab)
- nvd.nist.gov/vuln/detail/CVE-2021-3199 (opens in a new tab)
- cisa.gov/known-exploited-vulnerabilities-catalog?search=CVE-2021-3199 (opens in a new tab)