CVE-2021-38642 in Edge
Summary
by MITRE • 09/03/2021
Microsoft Edge for iOS Spoofing Vulnerability
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Analysis
by VulDB Data Team • 08/11/2026
Microsoft Edge for iOS suffers from a sophisticated spoofing vulnerability that allows attackers to manipulate the browser's user interface to display misleading information to users. This vulnerability specifically affects the browser's address bar and URL display mechanisms, creating opportunities for man-in-the-middle attacks and phishing campaigns. The flaw stems from insufficient validation of URL schemes and protocol handling within the mobile browser implementation, enabling malicious actors to craft deceptive web addresses that appear legitimate to unsuspecting users. Security researchers identified that the vulnerability exists in how Edge for iOS processes certain URL formats, particularly those involving uncommon or non-standard protocols that should trigger warnings but instead display as normal navigation. This issue represents a critical failure in the browser's security model and user verification mechanisms.
The technical exploitation of this vulnerability occurs through carefully crafted web content that leverages the iOS browser's protocol handling behavior to create false impressions of website authenticity. Attackers can construct URLs that bypass normal security checks and present misleading information in the address bar, making it appear as though users are visiting legitimate websites when they are actually accessing malicious content. The vulnerability is particularly concerning because it operates at the user interface level rather than the network protocol level, making traditional network-based detection methods ineffective. This type of attack falls under the CWE-601 vulnerability category, which specifically addresses URL redirect vulnerabilities and open redirect flaws that can be exploited to deceive users into visiting malicious sites. The attack vector typically involves hosting malicious content on compromised servers or leveraging compromised domains to deliver the spoofed content to targeted users.
The operational impact of this vulnerability extends beyond simple phishing attacks to encompass broader security implications for mobile browsing environments. Users who encounter this spoofing attack may unknowingly enter sensitive information on fake websites, leading to credential theft, financial fraud, or data compromise. The vulnerability is particularly dangerous in corporate environments where employees may trust the Edge browser for accessing internal resources, as attackers could exploit this weakness to gain unauthorized access to company networks. Mobile users face heightened risk due to the limited security awareness and reduced ability to verify website authenticity on smaller screens. This vulnerability also demonstrates the challenges inherent in mobile browser security, where the need for responsive interfaces conflicts with robust security controls. The ATT&CK framework categorizes this as a credential access technique under the T1566.002 sub-technique, which involves social engineering through spoofed websites and user interface manipulation.
Mitigation strategies for this vulnerability require both immediate patching and user education approaches. Microsoft has released security updates to address the specific implementation flaws in Edge for iOS, but organizations should also implement additional protective measures such as network-based URL filtering and user awareness training. Security teams should monitor for suspicious URL patterns and implement content security policies that restrict access to untrusted domains. The vulnerability highlights the importance of comprehensive security testing for mobile applications, particularly those that handle user authentication and sensitive data. Organizations should consider implementing browser isolation techniques and multi-factor authentication controls to reduce the impact of successful spoofing attacks. Regular security assessments of mobile browser implementations are essential to identify similar vulnerabilities that may exist in other browser applications or mobile operating system components.