PatchTheCVECVE-2021-3199: ONLYOFFICE Docs Server Path Traversal Vulnerability
CVE-2021-3199 is a critical-severity flaw (CVSS 9.8) affecting document server, reported as exploited in the wild. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.
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.
Why this priority
- Critical severity
- EPSS top 3%: very likely to be exploited
- Exploited in the wild (CISA KEV)
- Public exploit reference
- CISA SSVC: automatable with total technical impact
- Remotely exploitable, no login, no user action
A fixed release or distro patch exists.
Risk facts
| CVSS score | 9.8 (Critical) |
| Attack vector | Network (remote) |
| Attack complexity | Low |
| Privileges needed | None |
| User interaction | None |
| EPSS exploit chance | 20.1% (top 3%) |
| CISA exploited list | Yes, fix due 2026-10-11 |
| Weakness | CWE-22 |
| Published | 2021-01-26 |
| Last modified | 2026-10-09 |
Last updated 2026-10-09 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score
Am I affected?
Timeline
- Published CVE record published
- Exploited Added to the CISA Known Exploited Vulnerabilities list
- Updated Record last modified
- Deadline CISA due date for US federal agencies to patch
Exact fixes by distribution
Public exploits and detection
Public code exists for this CVE. Treat unpatched systems as at risk, and only run PoCs in a lab.
- Write-up: github.com/moehw/poc_exploits/tree/master/CVE-2021-3199/poc_uploadImageFile.py
- Write-up: github.com/nola-milkin/poc_exploits/blob/master/CVE-2021-3199/poc_uploadImageFile.py
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.
Quick answers
How do I fix CVE-2021-3199?
document server: upgrade to 5.6.3. Exact commands for each OS are on this page.
Is CVE-2021-3199 being exploited?
Yes. CVE-2021-3199 is on the CISA Known Exploited Vulnerabilities list, so treat it as patch-now.
What does CVE-2021-3199 affect?
CVE-2021-3199 affects document server. Severity is critical (CVSS 9.8). 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.
How urgent is CVE-2021-3199?
Priority 97/100. Critical severity; EPSS top 3%: very likely to be exploited; Exploited in the wild (CISA KEV); Public exploit reference; CISA SSVC: automatable with total technical impact; Remotely exploitable, no login, no user action