Strategic Overview
- Status
- Patched in 3.3.13
- Affected Plugin
- Tatsu
- Affected Version
<= 3.3.12- CVSS
- 6.5Medium
- Weakness type
- CWE-434 · Unrestricted Upload of File with Dangerous Type
- CVE
CVE-2021-25094
At a glance
CVE-2021-25094 is a medium-severity Unrestricted Upload of File with Dangerous Type vulnerability in the Tatsu WordPress plugin, affecting versions <= 3.3.12. It carries a CVSS score of 6.5 (reachable over the network; low attack complexity). Exploitation requires no authentication. The issue is fixed in version 3.3.13; sites on affected versions should update now. Disclosed March 2022, reported by Vincent MICHEL.
Vulnerability Overview
The Tatsu WordPress plugin before 3.3.13 add_custom_font action can be used without prior authentication to upload a rogue zip file which is uncompressed under the WordPress's upload directory. By adding a PHP shell with a filename starting with a dot ".", this can bypass extension control implemented in the plugin. Moreover, there is a race condition in the zip extraction process which makes the shell file live long enough on the filesystem to be callable by an attacker.
Technical Analysis
The vector marks this flaw as remotely reachable over the network, with low attack complexity — no special timing or configuration is needed, and no privileges on the target site, and no interaction from a victim user.
CWE-434: Unrestricted Upload of File with Dangerous Type
Reaching this weakness in Tatsu <= 3.3.12 takes no account at all. An unrestricted file upload lets a caller store a file whose type or destination the application does not properly constrain.
If an uploaded file lands anywhere the server will execute, the flaw becomes remote code execution and the site should be treated as fully compromised. For Tatsu the fix is 3.3.13: builds <= 3.3.12 are affected, anything from 3.3.13 onward is not.
Remediation
Update to version 3.3.13, or a newer patched version
How does WordSec protect against this?
Requests carrying this pattern arrive without a session, so nothing upstream of the firewall gets a chance to reject them: WordSec's web application firewall inspects request payloads before WordPress loads them. Classes like this one can leave something behind, so the staged malware scanner is the second half: it looks for dropped files and modified code rather than for the request that created them. None of that substitutes for the fix: Tatsu 3.3.13 closes this, and updating the plugin is the step that ends it.
- Firewall
- Scanner
- Login Security
External References
Vulnerability data © Defiant, Inc., provided under the Wordfence Intelligence T&C