Critical severity · published Jan 22, 2021
CVE-2021-3199
ONLYOFFICE Docs Server Path Traversal Vulnerability
In wildKEV
9.8
CVSS
30.2%
EPSS
Yes
On KEV
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.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Confidentiality
High
Integrity
High
Availability
High
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)30.2% · higher than 98% of CVEs
Exploited in the wildYes
CISA KEVListed Oct 8, 2026
Federal remediation dueOct 11, 2026
Ransomware campaign useNot known
Affected products
Which versions
DS
Document Server · Onlyoffice
before 5.6.3 · source: NVD
DO
Docs · ONLYOFFICE
All versions, or not specified · source: KEV
In the news
AdvisoryHigh
Chinese Government-linked Cyber Threat Actors Combine Automated and Hands-on Hacking Tools to Steal Sensitive Data
Advisory at a Glance
Title
Chinese Government-linked Cyber Threat Actors Combine Automated and Hands-on Hacking Tools to Steal Sensitive Data
Original Publication
October 8, 2026
Executive Summary
Chinese government-linked cyber threat actors, enabled by the Integrity Technology Group, are combining automated scanning tools, large-scale botnets, and hands-on exploitation techniques to target and steal sensitive data from organizations worldwide, including US critical infrastructure sectors. These actors exploit vulnerabilities by using scanning tools, cross-site scripting attacks, and password spraying on Microsoft Exchange servers, while establishing persistence through VPN software and exfiltrating emails and credentials using scripts. To help mitigate against this activity, organizations should prioritize disabling unused services and ports, sanitizing web application inputs to prevent injection attacks, implementing multifactor authentication for all services, and applying timely patches to reduce risks of compromise.
Affected Products
CVE-2014-6278
CVE-2015-3306
CVE-2015-5477
CVE-2016-3081
CVE-2019-11510
CVE-2021-22205
CVE-2021-3199
CVE-2023-22894
Key Actions
...
Oct 8, 2026·CISA Advisories
VulnerabilityCritical
[CISA KEV] CVE-2021-3199: ONLYOFFICE Docs - ONLYOFFICE Docs Server Path Traversal Vulnerability
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.
DODocsCVE-2021-3199
Oct 8, 2026·CISA KEV
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2021-3199
CVE.org
https://www.cve.org/CVERecord?id=CVE-2021-3199
CISA KEV catalogue
https://www.cisa.gov/known-exploited-vulnerabilities-catalog
x_refsource_CONFIRM
https://github.com/ONLYOFFICE/DocumentServer/blob/903fe5ab7a275bd69c3c3346af2d21cf87ebeabf/CHANGELOG.md#563
x_refsource_MISC
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
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