CVE-2021-21201 in Chrome
Summary
by MITRE • 04/26/2021
Use after free in permissions in Google Chrome prior to 90.0.4430.72 allowed a remote attacker who had compromised the renderer process to potentially perform a sandbox escape via a crafted HTML page.
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Analysis
by VulDB Data Team • 04/30/2021
The vulnerability identified as CVE-2021-21201 represents a critical use-after-free condition within Google Chrome's permission handling mechanisms that existed prior to version 90.0.4430.72. This flaw manifests in the browser's renderer process and creates a pathway for remote attackers to potentially escape the sandbox environment that normally isolates browser components from the underlying operating system. The vulnerability stems from improper memory management where freed memory locations are still being accessed or referenced, creating a condition that can be exploited to execute arbitrary code with elevated privileges.
The technical implementation of this vulnerability involves a specific race condition or memory management error within Chrome's permission system that allows an attacker to manipulate the browser's memory state. When a crafted HTML page is loaded, it can trigger a sequence where memory allocated for permission handling is freed but subsequently accessed by malicious code. This use-after-free condition creates a memory corruption scenario that can be leveraged to gain control over the browser's execution flow. The flaw specifically affects the renderer process which is designed to run in a restricted environment separate from the main browser process, but the vulnerability allows for potential escalation of privileges.
From an operational perspective, this vulnerability presents a significant risk to users as it requires only a malicious webpage to compromise a system. The attack vector is particularly dangerous because it targets the renderer process, which is already trusted to execute potentially malicious content from the web. Attackers who have already gained access to a compromised renderer process can exploit this flaw to break out of the sandbox containment and potentially execute code with the privileges of the user account running Chrome. This could lead to full system compromise, data theft, or further lateral movement within a network. The vulnerability aligns with CWE-416, which specifically addresses use-after-free errors in memory management, and represents a classic sandbox escape technique that violates the fundamental security model of modern browsers.
The impact of this vulnerability extends beyond individual user compromise to broader security implications for enterprise environments where Chrome is widely deployed. Organizations that rely on Chrome for web browsing activities face potential exposure to sophisticated attacks that could bypass traditional security controls. The vulnerability demonstrates the ongoing challenge in maintaining secure browser environments where complex permission systems must balance usability with security. Mitigation strategies include immediate patching to version 90.0.4430.72 or later, along with enhanced monitoring for suspicious browser behavior and network traffic patterns. Security teams should also consider implementing additional browser hardening measures and network-based protections to reduce the attack surface. This vulnerability also highlights the importance of continuous security assessment and the need for robust memory safety practices in browser development, aligning with ATT&CK technique T1059.007 for browser-based attacks and T1106 for execution through system commands. The flaw serves as a reminder of the critical importance of maintaining up-to-date software and the potential consequences of relying on outdated browser versions in enterprise security architectures.