The software constructs pathnames from user input, but it does not properly handle when the pathname contains a Windows device name such as AUX or CON. This typically leads to denial of service or an information leak when the application attempts to process the pathname as a regular file.

Failing to properly handle virtual filenames (e.g. AUX, CON, PRN, COM1, LPT1) can result in different types of vulnerabilities. In some cases an attacker can request a device via injection of a virtual filename in a URL, which may cause an error that leads to a denial of service or an error page that reveals sensitive information. A software system that allows device names to bypass filtering runs the risk of an attacker injecting malicious code in a file with the name of a device.