CVE-2021-21221 in Chrome
Summary
by MITRE • 04/26/2021
Insufficient validation of untrusted input in Mojo in Google Chrome prior to 90.0.4430.72 allowed a remote attacker who had compromised the renderer process to leak cross-origin data via a crafted HTML page.
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Analysis
by VulDB Data Team • 04/30/2021
The vulnerability CVE-2021-21221 represents a critical security flaw in Google Chrome's Mojo framework that existed prior to version 90.0.4430.72. This issue stems from insufficient validation of untrusted input within the Mojo component system, which serves as a foundational communication layer for Chrome's architecture. The vulnerability specifically affects the renderer process and creates a pathway for remote attackers to exploit cross-origin data leakage through carefully crafted HTML pages. The Mojo framework is designed to facilitate efficient communication between different Chrome processes while maintaining security boundaries, but this flaw undermines those protective mechanisms.
The technical implementation of this vulnerability leverages the renderer process compromise as a prerequisite for exploitation, aligning with attack patterns described in the ATT&CK framework under process injection and privilege escalation techniques. When an attacker successfully compromises the renderer process, they can manipulate the Mojo communication channels to bypass normal security restrictions. The insufficient input validation allows malicious HTML content to inject crafted data that can traverse security boundaries between different origins, effectively enabling cross-origin information leakage. This flaw operates at the intersection of multiple security domains including browser architecture, process isolation, and inter-process communication protocols.
The operational impact of CVE-2021-21221 extends beyond simple data leakage, as it represents a significant bypass of Chrome's security model that could enable more sophisticated attacks. Attackers could potentially access sensitive information from other origins, including cookies, local storage data, and potentially even user credentials or personal information. The vulnerability's classification under CWE-20 indicates a weakness in input validation, specifically where untrusted data is not properly validated before being processed by the Mojo framework. This creates a dangerous scenario where an attacker with renderer-level access can leverage the framework's communication capabilities to extract data that should normally be isolated between different security contexts.
Mitigation strategies for this vulnerability require immediate patching of Chrome to version 90.0.4430.72 or later, which contains the necessary fixes for the input validation issues in the Mojo framework. Organizations should implement comprehensive monitoring for suspicious renderer process activities and ensure that all Chrome installations are kept current with security updates. The remediation process should also include reviewing existing security policies to ensure that renderer process isolation remains intact and that no additional attack vectors have been introduced through browser configuration changes. Additionally, security teams should consider implementing network-based detection mechanisms that can identify unusual cross-origin data access patterns that might indicate exploitation attempts.