CVE-2021-3199: ONLYOFFICE Docs Server Path Traversal Vulnerability
Advisory generated from the CVE record, CISA, Exploit Observer and VEDAS: what it is, whether it is exploited, who is affected, and how to fix and detect it.
Generated by VEDAS. Scores as of 2026-11-01 19:19 UTC. Rebuilt every few hours from cve-scores, CISA KEV and vedas-signatures. How this works and its limits.
What it is
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.
Description quoted from the CVE record (assigned by mitre, published 2021-01-22).
Weakness: CWE-22 Improper Limitation of a Pathname to a Restricted Directory (‘Path Traversal’)
How it can be exploited
Exploitable over the network with low attack complexity needing no privileges and no user interaction. Impact: confidentiality high, integrity high, availability high. CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
CISA assessment (SSVC): CISA assesses exploitation as active. Automatable: yes. Technical impact: total.
- On CISA KEV since
- 2026-10-08
- US federal deadline
- 2026-10-11
- Ransomware use
- Not known
Public exploit evidence (Exploit Observer)
Also known as: BDU:2026-16230, CNNVD-202101-2236, CNVD-2021-17251, EUVD-2021-26539, GHSA-vm8r-r39c-96c6
Exploit Observer has no public exploit code that names this CVE or one of its aliases.
Vulnerability databases and vendor advisories (7)
Catalogue entries, not exploit evidence.
- Vulnerability database or vendor advisory: https://euvd.enisa.europa.eu/enisa/EUVD-2021-26539
- Vulnerability database or vendor advisory: https://github.com/advisories/GHSA-vm8r-r39c-96c6
- Vulnerability database or vendor advisory: https://nvd.nist.gov/vuln/detail/CVE-2021-3199
- Vulnerability database or vendor advisory: https://osv.dev/vulnerability/CVE-2021-3199
- Vulnerability database or vendor advisory: https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-3199
- Vulnerability database or vendor advisory: https://www.cnnvd.org.cn/home/globalSearch?keyword=CNNVD-202101-2236
- Vulnerability database or vendor advisory: https://www.cnvd.org.cn/flaw/show/CNVD-2021-17251
4 more references returned by Exploit Observer did not name this CVE or an alias, so they are left out.
VEDAS data as of 2026-11-01T17:12 UTC; fetched 2026-11-02.
Live scores
- EPSS
- 0.302
likely to be attacked soon - VEDAS
- 0.587
some exploit evidence - On CISA KEV
- Yes, since 2026-10-08
- Detection rule
- None yet
Thin horizontal line: the “likely” (EPSS 0.10) or “strong” (VEDAS 0.90) threshold. Shaded “no data” areas are periods when cve-scores did not publish. The vertical line is the day CISA added it to its exploited list.
Who is affected
| Product | Affected | Not affected |
|---|---|---|
| Not stated | version n/a | Not stated |
Version ranges exactly as the CVE record states them. “Before X” means X is the first fixed version.
How to fix it
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.
Vendor guidance:
- https://github.com/ONLYOFFICE/DocumentServer/blob/903fe5ab7a275bd69c3c3346af2d21cf87ebeabf/CHANGELOG.md#563
- https://www.cisa.gov/news-events/directives/bod-26-04-prioritizing-security-updates-based-risk
- 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
How to detect it
There is no open VEDAS detection rule for this bug yet. It is listed on the detection gaps page if CISA has confirmed attacks.
Advisories on this CVE
References
Government sources
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-3199 (government-resource)
Other references
- https://github.com/ONLYOFFICE/DocumentServer/blob/903fe5ab7a275bd69c3c3346af2d21cf87ebeabf/CHANGELOG.md#563 (x_refsource_CONFIRM)
- https://github.com/nola-milkin/poc_exploits/blob/master/CVE-2021-3199/poc_uploadImageFile.py (x_refsource_MISC)
- https://github.com/moehw/poc_exploits/tree/master/CVE-2021-3199/poc_uploadImageFile.py (x_refsource_MISC)
Other databases
Where this comes from
This advisory is generated automatically by VEDAS from: CVE.org record, CISA KEV, cve-scores (EPSS and VEDAS), Exploit Observer. Text in quotes is reproduced from the source; everything else is a fixed template filled with source fields. Nothing here is written by a language model. Check the vendor advisory before acting, and read how VEDAS and Exploit Observer work, and their limits.