In YARA 3.8.1, bytecode in a specially crafted compiled rule can read data from any arbitrary address in memory, in libyara/exec.c. Specifically, OPCOUNT can read a DWORD.

An exploitable denial of service vulnerability exists in the object lookup functionality of Yara 3.8.1. A specially crafted binary file can cause a negative value to be read to satisfy an assert, resulting in Denial of Service. An attacker can create a malicious binary to trigger this vulnerability.

In YARA 3.8.1, bytecode in a specially crafted compiled rule can read uninitialized data from VM scratch memory in libyara/exec.c. This can allow attackers to discover addresses in the real stack (not the YARA virtual stack).

In YARA 3.8.1, bytecode in a specially crafted compiled rule is exposed to information about its environment, in libyara/exec.c. This is a consequence of the design of the YARA virtual machine.