CVE-2021-21170: 
vulnerability analysis and mitigation

CVE-2021-21170 is a security vulnerability discovered in Google Chrome prior to version 89.0.4389.72. The vulnerability was identified as an incorrect security UI implementation in the Loader component, reported by David Erceg on July 31, 2020. This medium severity vulnerability allowed a remote attacker who had compromised the renderer process to spoof the contents of the Omnibox (URL bar) via a crafted HTML page (Chrome Release).

The vulnerability has been assigned a CVSS v3.1 Base Score of 6.5 (Medium), with the vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:N. This indicates that the vulnerability can be exploited remotely, requires low attack complexity, needs no privileges, but does require user interaction. The scope is unchanged, with no impact on confidentiality, high impact on integrity, and no impact on availability (NVD).

The vulnerability could allow an attacker who has already compromised the renderer process to manipulate the URL display in the browser's address bar, potentially enabling sophisticated phishing attacks by making malicious pages appear to come from legitimate sources (NVD).

The vulnerability requires the attacker to first compromise the renderer process and then craft a specific HTML page to exploit the security UI issue. The exploitation complexity is considered low, though it requires user interaction (NVD).

The vulnerability was patched in Google Chrome version 89.0.4389.72. Users and administrators are advised to upgrade to this version or later. The fix has been incorporated into various Linux distributions including Debian, Fedora, and Gentoo through their respective security updates (Debian Security, Gentoo Security).