CVE-2020-6555: 
Google Chrome vulnerability analysis and mitigation

CVE-2020-6555 is an out-of-bounds read vulnerability discovered in the WebGL functionality of Google Chrome versions prior to 84.0.4147.125. The vulnerability was reported by Marcin Towalski of Cisco Talos on July 13, 2020, and was patched in the stable channel update released on August 10, 2020 (Chrome Release, Talos Report).

The vulnerability exists in ANGLE, a compatibility layer between OpenGL and Direct3D used by Chrome browser on Windows. The issue occurs in the ConvertIndexArray function within IndexDataManager where unchecked boundaries for offset and count values from JavaScript can lead to an out-of-bounds read. The vulnerability was assigned a CVSS v3.1 base score of 7.6 HIGH (CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:L/A:L) and is classified as CWE-125 (Out-of-bounds Read) (NVD, Talos Report).

When exploited, this vulnerability allows a remote attacker to obtain potentially sensitive information from process memory via a crafted HTML page. The successful exploitation requires user interaction as the victim must visit a specially crafted malicious web page (NVD, Talos Report).

The vulnerability can be triggered through specially crafted JavaScript code that manipulates the DrawElementsInstanced function. The values provided for the offset variable in JavaScript can range from 00000000 to 7fffffff, and when combined with an unchecked count value, can lead to an out-of-bounds read condition (Talos Report).

The vulnerability was patched in Google Chrome version 84.0.4147.125. Users are advised to upgrade to this version or later to mitigate the risk. The fix was also incorporated into various Linux distributions including Fedora, Debian, and Gentoo through their respective security updates (Chrome Release, Fedora Update, Debian Update).