CVE-2023-1393

A vulnerability was found in X.Org Server. This flaw occurs if a client explicitly destroys the compositor overlay window (aka COW), where Xserver leaves a dangling pointer to that window in the CompScreen structure, which will later trigger a use-after-free issue. The Overlay Window use-after-free issue can lead to a local privilege escalation vulnerability.

This vulnerability allows local attackers to escalate privileges on affected installations of X.Org Server. An attacker must first obtain the ability to execute low-privileged code on the target system in order to exploit this vulnerability.
The specific flaw exists within the handling of overlay windows. The issue results from the lack of validating the existence of an object prior to performing operations on the object. An attacker can leverage this vulnerability to escalate privileges and execute arbitrary code in the context of root.

Virtual Network Computing is a remote display system which allows users to view a computing desktop environment not only on the machine where it is running, but from anywhere on the Internet and from a wide variety of machine architectures. TigerVNC is a suite of VNC servers and clients. X.Org is an open-source implementation of the X Window System. It provides the basic low-level functionality that full-fledged graphical user interfaces are designed upon. Issues addressed include privilege escalation and use-after-free vulnerabilities.