CVE-2021-21216 in Chrome
Summary
by MITRE • 04/26/2021
Inappropriate implementation in Autofill in Google Chrome prior to 90.0.4430.72 allowed a remote attacker to spoof security UI via a crafted HTML page.
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Analysis
by VulDB Data Team • 04/30/2021
The vulnerability identified as CVE-2021-21216 represents a critical security flaw in Google Chrome's Autofill implementation that existed prior to version 90.0.4430.72. This issue falls under the broader category of user interface spoofing attacks, where malicious actors can manipulate the browser's security indicators to deceive users into believing they are interacting with legitimate websites. The vulnerability specifically targets Chrome's autofill functionality which is designed to streamline user experience by automatically filling forms with saved credentials, personal information, and other data. The flaw allows remote attackers to craft malicious HTML pages that can manipulate the browser's security UI elements, potentially leading users to unknowingly submit sensitive information to fraudulent sites.
The technical implementation flaw stems from insufficient validation and sanitization of HTML content within Chrome's autofill system. When users navigate to crafted web pages, the malicious code can exploit the browser's rendering engine to alter or replace legitimate security indicators such as URL bar displays, certificate information, or other visual cues that typically alert users to potential security risks. This allows attackers to create convincing facsimiles of trusted websites while bypassing the normal security mechanisms that would otherwise protect users. The vulnerability operates at the intersection of web browser security architecture and user interface design, where the line between legitimate functionality and malicious manipulation becomes blurred. The implementation error specifically affects how Chrome processes and displays security-related UI elements during autofill operations, creating a window of opportunity for attackers to exploit the trust relationship between users and their browsers.
The operational impact of this vulnerability extends beyond simple credential theft, encompassing a broader range of potential attacks that leverage user trust in browser security features. Attackers can craft sophisticated phishing campaigns where victims are deceived into entering sensitive data such as passwords, credit card numbers, or personal identification information. The vulnerability is particularly dangerous because it operates at the user interface level, making it difficult for users to distinguish between legitimate and malicious interactions. Security researchers have noted that this type of attack can be particularly effective in social engineering campaigns where attackers have already established some level of trust with their targets. The vulnerability also represents a significant concern for enterprise environments where users may unknowingly compromise sensitive corporate data through seemingly legitimate browser interactions. This flaw can be exploited in various attack scenarios including man-in-the-middle attacks, credential harvesting, and data exfiltration operations that rely on user deception.
Mitigation strategies for CVE-2021-21216 primarily focus on immediate software updates and enhanced security monitoring. Organizations should prioritize updating Chrome installations to version 90.0.4430.72 or later, which contains the necessary patches to address the vulnerability. Browser security teams should implement additional monitoring of user interactions with autofill features and establish protocols for detecting unusual patterns that might indicate spoofing attempts. Network security solutions should be configured to monitor for suspicious HTML content and potentially malicious web page behaviors that could indicate exploitation attempts. Users should be educated about the importance of verifying website authenticity before entering sensitive information and should be trained to recognize subtle differences in browser security indicators. The vulnerability also highlights the importance of maintaining up-to-date browser security practices and the need for continuous monitoring of security advisories. Security professionals should consider implementing additional layers of protection such as browser security extensions, enhanced web filtering, and user behavior analytics to detect and prevent exploitation attempts. This vulnerability serves as a reminder of the critical importance of maintaining robust browser security implementations and the potential consequences when user interface security mechanisms are compromised.