CVE-2020-13543: 
NixOS vulnerability analysis and mitigation

A code execution vulnerability exists in the WebSocket functionality of Webkit WebKitGTK 2.30.0. The vulnerability, identified as CVE-2020-13543, was discovered in 2020 and affects the WebSocket implementation in WebKitGTK browser engine. A specially crafted web page can trigger a use-after-free vulnerability which can lead to remote code execution (Talos Report, Debian Tracker).

The vulnerability is related to the WebSocket variable handling during document reloads. When a malicious web page creates a WebSocket object and manipulates its event handlers during closure, it can trigger a use-after-free condition. The vulnerability received a CVSSv3 score of 8.8 (CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H) and is classified as CWE-416 (Use After Free). The issue occurs specifically when the WebSocket object is released while handling certain document operations (Talos Report).

If successfully exploited, this vulnerability could allow an attacker to execute arbitrary code on the target system. The impact is severe as it could lead to complete system compromise, with the attacker gaining the same privileges as the WebKit process. Proper heap grooming can give an attacker full control of this use-after-free vulnerability (Talos Report).

The vulnerability can be triggered by enticing a user to visit a specially crafted webpage. An attacker needs to create a malicious web page that exploits the WebSocket functionality to trigger the use-after-free condition. The attack requires user interaction but is relatively straightforward to exploit given the technical details available (Talos Report).

The vulnerability has been fixed in WebKitGTK version 2.30.3. Users are advised to upgrade to this version or later. Debian has released security updates through DSA-4797-1, and various other distributions have also provided patches. For systems that cannot be immediately updated, there is no known workaround (Debian Tracker, Gentoo Security).