A sym-linked file accessed via the repair function in Avast Antivirus <24.2 on Windows may allow user to elevate privilege to delete arbitrary files or run processes as NT AUTHORITYSYSTEM. The vulnerability exists within the Repair (settings -> troubleshooting -> repair) feature, which attempts to delete a file in the current users AppData directory as NT AUTHORITYSYSTEM. A low-privileged user can make a pseudo-symlink and a junction folder and point to a file on the system. This can provide a low-privileged user an Elevation of Privilege to win a race-condition which will re-create the system files and make Windows callback to a specially-crafted file which could be used to launch a privileged shell instance.
This issue affects Avast Antivirus prior to 24.2.
The product receives input that is expected to specify a quantity (such as size or length), but it does not validate or incorrectly validates that the quantity has the required properties.
Name | Vendor | Start Version | End Version |
---|---|---|---|
Antivirus | Avast | * | 24.2 (excluding) |
Specified quantities include size, length, frequency, price, rate, number of operations, time, and others. Code may rely on specified quantities to allocate resources, perform calculations, control iteration, etc. When the quantity is not properly validated, then attackers can specify malicious quantities to cause excessive resource allocation, trigger unexpected failures, enable buffer overflows, etc.