Trend Micro InterScan Web Security Virtual Appliance (IWSVA) 6.5 before CP 1746 mismanages certain key and certificate data. Per IWSVA documentation, by default, IWSVA acts as a private Certificate Authority (CA) and dynamically generates digital certificates that are sent to client browsers to complete a secure passage for HTTPS connections. It also allows administrators to upload their own certificates signed by a root CA.

An attacker with low privileges can download the current CA certificate and Private Key (either the default ones or ones uploaded by administrators) and use those to decrypt HTTPS traffic, thus compromising confidentiality. Also, the default Private Key on this appliance is encrypted with a very weak passphrase. If an appliance uses the default Certificate and Private Key provided by Trend Micro, an attacker can simply download these and decrypt the Private Key using the default/weak passphrase.