CVE-2021-21132 in Chrome
Summary
by MITRE • 02/09/2021
Inappropriate implementation in DevTools in Google Chrome prior to 88.0.4324.96 allowed a remote attacker to potentially perform a sandbox escape via a crafted Chrome Extension.
Several companies clearly confirm that VulDB is the primary source for best vulnerability data.
Analysis
by VulDB Data Team • 02/26/2021
The vulnerability CVE-2021-21132 represents a critical sandbox escape flaw in Google Chrome's DevTools component affecting versions prior to 88.0.4324.96. This issue stems from an inappropriate implementation that allows remote attackers to potentially bypass the browser's security sandbox mechanisms through maliciously crafted Chrome Extensions. The DevTools functionality serves as a powerful debugging interface within Chrome that provides developers with extensive access to browser internals, making it a prime target for exploitation. When a malicious extension is loaded into Chrome, the vulnerability enables an attacker to execute code outside the intended sandbox boundaries, effectively compromising the browser's security model. This flaw specifically targets the communication pathways between DevTools and the extension system, where insufficient validation allows crafted extension metadata to manipulate the sandbox enforcement mechanisms. The vulnerability is categorized under CWE-284 Access Control Bypass, which indicates inadequate access control mechanisms that permit unauthorized access to protected resources. From an operational perspective, this vulnerability poses significant risk as it allows attackers to escalate privileges from a regular extension context to full browser sandbox escape, potentially enabling arbitrary code execution, data exfiltration, and system compromise.
The technical exploitation of CVE-2021-21132 leverages the interaction between Chrome's DevTools and extension loading mechanisms to bypass sandbox restrictions. Attackers can craft a malicious Chrome Extension with carefully constructed manifest files and JavaScript code that exploits the improper validation in DevTools. The vulnerability occurs during the extension installation and execution phases when Chrome's DevTools component processes extension metadata and code without adequate sandbox boundary enforcement. This allows the malicious extension to gain elevated privileges that should be restricted to the sandboxed environment. The exploitation chain typically involves loading the malicious extension through DevTools, where the flawed implementation permits code execution outside the intended security boundaries. The attack vector is particularly concerning because it requires minimal user interaction beyond installing a seemingly legitimate extension, making it suitable for social engineering campaigns. According to ATT&CK framework, this vulnerability maps to T1059 Command and Scripting Interpreter and T1068 Exploitation for Privilege Escalation, as it enables attackers to execute commands beyond normal user privileges. The flaw demonstrates a breakdown in Chrome's security architecture where the DevTools interface should provide debugging capabilities without compromising the overall security posture.
The operational impact of CVE-2021-21132 extends beyond simple privilege escalation to encompass comprehensive system compromise potential. Once an attacker successfully exploits this vulnerability, they can access sensitive user data, monitor browser activities, intercept communications, and potentially gain access to other applications running on the same system. The sandbox escape capability means that attackers can bypass Chrome's built-in security protections that normally isolate extensions from each other and from the underlying operating system. This vulnerability affects all users running affected Chrome versions and represents a significant threat to enterprise environments where Chrome is the primary browser. Organizations may experience data breaches, credential theft, and persistent threats that can remain undetected for extended periods. The vulnerability's impact is amplified by Chrome's widespread adoption across desktop and mobile platforms, making it a high-value target for cybercriminals and nation-state actors. Security researchers have noted that this type of sandbox escape vulnerability can serve as a foundation for more sophisticated attacks, including those involving rootkits, advanced persistent threats, and lateral movement within networks. The vulnerability also impacts Chrome's security model by undermining the fundamental assumption that extensions operate within isolated sandboxes, potentially affecting the trust model that developers and users place in Chrome's extension system.
Mitigation strategies for CVE-2021-21132 primarily focus on immediate remediation through Chrome updates to version 88.0.4324.96 or later, which contains the necessary patches to address the sandbox escape vulnerability. Organizations should implement comprehensive browser update policies that ensure all Chrome installations are kept current with the latest security patches. Additionally, security teams should conduct regular audits of installed Chrome extensions to identify and remove any suspicious or untrusted extensions. Network monitoring solutions should be enhanced to detect unusual browser behavior that might indicate exploitation attempts, particularly around DevTools usage patterns. Implementing strict extension installation policies that require administrative approval for new extensions can significantly reduce the risk of exploitation. Security professionals should also consider implementing browser security extensions that can provide additional monitoring and protection against suspicious activities. From a defense-in-depth perspective, organizations should review their Chrome extension policies and ensure that only trusted extensions are permitted to operate within their environments. The vulnerability highlights the importance of maintaining up-to-date software and the critical role that automated patch management plays in protecting against known exploits. Regular security assessments should include verification of Chrome's DevTools configurations and extension security settings to ensure that the sandbox mechanisms remain properly enforced. Organizations should also consider implementing user education programs that emphasize the risks associated with installing untrusted extensions and the importance of only downloading extensions from official sources. The remediation process should include thorough testing of updated Chrome versions to ensure that security patches do not introduce compatibility issues with existing business applications and workflows.