Vulnerability · Published Aug 25, 2021 · Assigned by mitre
CVE-2021-37334
Critical 9.8
In plain English
A critical-severity security flaw in the affected software. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 2.7% (higher than 86% of all known vulnerabilities).
Official description
Umbraco Forms version 4.0.0 up to and including 8.7.5 and below are vulnerable to a security flaw that could lead to a remote code execution attack and/or arbitrary file deletion. A vulnerability occurs because validation of the file extension is performed after the file has been stored in a temporary directory. By default, files are stored within the application directory structure at %BASEDIR%/APP_DATA/TEMP/FileUploads/. Whilst access to this directory is restricted by the root web.config file, it is possible to override this restriction by uploading another specially crafted web.config file to the temporary directory. It is possible to exploit this flaw to upload a malicious script file to execute arbitrary code and system commands on the server.