CVE-2020-6522 in Chrome
Summary
by MITRE
Inappropriate implementation in external protocol handlers in Google Chrome prior to 84.0.4147.89 allowed a remote attacker to potentially perform a sandbox escape via a crafted HTML page.
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Analysis
by VulDB Data Team • 05/05/2025
The vulnerability identified as CVE-2020-6522 represents a critical sandbox escape flaw in Google Chrome's handling of external protocol handlers. This issue affected Chrome versions prior to 84.0.4147.89 and stems from an inadequate implementation of how the browser processes external protocol schemes such as mailto, tel, or ftp. The flaw allows remote attackers to craft malicious HTML pages that can bypass Chrome's security sandbox mechanisms, potentially enabling them to execute arbitrary code on the target system with elevated privileges. The vulnerability specifically targets the browser's external protocol handler implementation, which is designed to manage user interactions with external applications through web-based links.
The technical nature of this vulnerability aligns with CWE-787, which describes out-of-bounds writes or memory corruption issues that can occur when applications fail to properly validate input data. In this case, the flaw manifests when Chrome processes external protocol URLs that contain crafted payloads, allowing attackers to manipulate the browser's execution flow and potentially escape the restricted sandbox environment. The vulnerability operates through a sophisticated attack chain that leverages the browser's trust in external protocol handlers to gain unauthorized access to system resources. Attackers can exploit this weakness by hosting malicious web content that triggers the vulnerable code path when users interact with specific external protocol links.
The operational impact of CVE-2020-6522 extends beyond simple privilege escalation, as it fundamentally undermines Chrome's security model by enabling sandbox escape capabilities. This vulnerability can be exploited in various attack scenarios including phishing campaigns, drive-by downloads, and targeted attacks against specific user groups. The sandbox escape capability allows attackers to bypass multiple security layers including the renderer sandbox, process isolation, and other Chromium security controls. This makes the vulnerability particularly dangerous as it can enable attackers to access sensitive user data, install malware, or perform further reconnaissance on the compromised system.
Mitigation strategies for this vulnerability primarily focus on immediate Chrome updates to versions 84.0.4147.89 or later where the issue has been patched. Organizations should implement comprehensive patch management procedures to ensure all Chrome installations are updated promptly. Additional defensive measures include implementing web application firewalls, monitoring for suspicious external protocol handler usage, and educating users about the risks of visiting untrusted websites. Security teams should also consider deploying browser security extensions and configuring Chrome's security policies to restrict external protocol handler behavior. The mitigation approach aligns with ATT&CK technique T1059.001 for command and scripting interpreter and T1068 for exploit for privilege escalation, emphasizing the need for layered defense mechanisms to protect against such sophisticated attacks. Organizations should also monitor for indicators of compromise related to external protocol handler abuse and maintain incident response procedures specifically addressing sandbox escape vulnerabilities.