CVE-2021-21134 in Chrome
Summary
by MITRE • 02/09/2021
Incorrect security UI in Page Info in Google Chrome on iOS prior to 88.0.4324.96 allowed a remote attacker to spoof security UI via a crafted HTML page.
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Analysis
by VulDB Data Team • 02/26/2021
The vulnerability identified as CVE-2021-21134 represents a critical security flaw in Google Chrome's implementation of the Page Info feature on iOS platforms. This issue specifically affects Chrome versions prior to 88.0.4324.96 and stems from improper handling of security user interface elements that are meant to protect users from malicious web content. The flaw allows remote attackers to manipulate the visual presentation of security indicators, potentially deceiving users about the trustworthiness of web pages they are visiting. The vulnerability resides in how Chrome renders security information within its UI components, particularly when displaying page details and certificate information to users.
This security weakness manifests through the manipulation of HTML content that can influence the display of security indicators within Chrome's Page Info interface. Attackers can craft malicious web pages that exploit the browser's handling of security UI elements, creating deceptive visual representations that appear to show legitimate security information while actually concealing malicious activities. The technical implementation flaw likely involves insufficient validation of HTML content within the security UI rendering pipeline, allowing crafted payloads to alter the visual presentation of security warnings and certificate details. This type of vulnerability directly impacts the browser's ability to provide accurate security context to users, undermining the fundamental trust model that secure browsing relies upon.
The operational impact of CVE-2021-21134 extends beyond simple visual deception, as it represents a potential vector for sophisticated phishing attacks and man-in-the-middle scenarios. Users who rely on Chrome's security UI to make informed decisions about website trustworthiness may be misled into believing they are interacting with legitimate secure sites when they are actually encountering malicious content. This vulnerability aligns with attack patterns described in the ATT&CK framework under the T1566 category for Phishing, specifically targeting the user's perception of security rather than directly exploiting system vulnerabilities. The flaw particularly affects iOS users who may be more susceptible to visual deception due to the mobile browsing environment and limited security context awareness compared to desktop users.
From a compliance and security standards perspective, this vulnerability relates to CWE-611 Improper Restriction of XML External Entity Reference and CWE-200 Information Exposure, as it involves improper handling of security-related information that can lead to information disclosure through user deception. The vulnerability also demonstrates characteristics consistent with CWE-352 Cross-Site Request Forgery in its ability to manipulate user interface elements through crafted web content. Organizations and users should consider implementing additional security measures such as network monitoring for suspicious page load patterns, user education about security UI verification practices, and regular browser updates to mitigate potential exploitation. The fix implemented in Chrome version 88.0.4324.96 likely involved enhanced validation of HTML content within security UI components and stricter enforcement of security context rendering protocols.
The broader implications of this vulnerability highlight the critical importance of user interface security in modern browsers, where visual deception can be as dangerous as technical exploitation. Mobile platforms present unique challenges for security UI implementation due to screen size constraints and user interaction patterns, making vulnerabilities like CVE-2021-21134 particularly concerning. Security professionals should recognize that user interface elements designed to provide security assurance must themselves be protected against manipulation, as these components form the primary means by which users make security decisions. This vulnerability serves as a reminder that security cannot be achieved through technical measures alone but must also account for human factors and the trust relationships between users and security systems. The remediation approach taken by Google demonstrates the importance of comprehensive security testing that includes user interface components, particularly those that directly influence user perception of security status.