CVEs / CVE-2021-3199
CVE-2021-3199: ONLYOFFICE Docs Server Path Traversal Vulnerability
- Known exploited in the CISA KEV catalog since 8 Oct 2026
- critical 9.8 CVSS 3.1 (NVD)
- EPSS 30.2% chance of exploitation in the next 30 days, higher than 98% of CVEs (30 Oct 2026)
- Last changed at its sources
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Summary
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.
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 and fixed versions
| Product | Affected | Fixed in |
|---|---|---|
| n/a n/a | n/a | — |
Exploitation
| In CISA KEV since | 8 Oct 2026 |
|---|---|
| Due date for US federal agencies | 11 Oct 2026 |
| Used in ransomware campaigns | Unknown |
| 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. |
Severity
| CVSS 3.1 | 9.8 criticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:HScored by NVD |
|---|---|
| Weakness | CWE-22 |
References
- CVE-2021-3199 on NVD
- CVE-2021-3199 in the CISA KEV catalog
- https://github.com/ONLYOFFICE/DocumentServer/blob/903fe5ab7a275bd69c3c3346af2d21cf87ebeabf/CHANGELOG.md#563 (cited by CISA)
- https://www.cisa.gov/news-events/directives/bod-26-04-prioritizing-security-updates-based-risk (cited by CISA)
- https://www.cisa.gov/news-events/directives/bod-26-04-implementation-guidance-prioritizing-security-updates-based-risk (cited by CISA)
- CVE-2021-3199 on OSV
- https://github.com/ONLYOFFICE/DocumentServer/blob/903fe5ab7a275bd69c3c3346af2d21cf87ebeabf/CHANGELOG.md#563 Release Notes, Third Party Advisory
- https://github.com/moehw/poc_exploits/tree/master/CVE-2021-3199/poc_uploadImageFile.py Exploit, Third Party Advisory
- https://github.com/nola-milkin/poc_exploits/blob/master/CVE-2021-3199/poc_uploadImageFile.py Exploit, Third Party Advisory
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-3199 US Government Resource
Sources
Exploitation status from the CISA Known Exploited Vulnerabilities catalog. EPSS scores from FIRST. Descriptions, severity and references from the National Vulnerability Database. Open-source package versions from OSV (CC-BY 4.0). Text is shown as each source states it; Stackurity does not edit it. Check the vendor's advisory before acting.
This product uses data from the NVD API but is not endorsed or certified by the NVD.