CVE-2021-33595 in Safe Browser
Summary
by MITRE • 08/11/2021
A address bar spoofing vulnerability was discovered in Safe Browser for iOS. Showing the legitimate URL in the address bar while loading the content from other domain. This makes the user believe that the content is served by a legit domain. A remote attacker can leverage this to perform address bar spoofing attack.
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Analysis
by VulDB Data Team • 08/16/2021
The address bar spoofing vulnerability identified as CVE-2021-33595 represents a critical security flaw in Safe Browser for iOS that undermines user trust and browser security assurances. This vulnerability operates by displaying a legitimate URL in the browser's address bar while simultaneously loading content from a different, potentially malicious domain. The deception occurs during the page loading process, creating a false sense of security for users who believe they are interacting with a trusted website. This type of attack exploits the fundamental trust users place in visual browser indicators, particularly the address bar which serves as the primary means of verifying website authenticity.
The technical implementation of this vulnerability stems from improper handling of domain validation during page rendering processes. When a user navigates to a website, the browser should verify that the content being displayed matches the domain indicated in the address bar. In Safe Browser for iOS, this validation mechanism fails, allowing content from one domain to be presented while the address bar displays a different domain. This discrepancy creates a window of opportunity for attackers to manipulate user perception and potentially execute phishing attacks or other social engineering schemes. The vulnerability falls under CWE-601 URL Redirection to Untrusted Site, which specifically addresses the risk of redirecting users to untrusted domains while maintaining the appearance of legitimacy.
The operational impact of this vulnerability extends beyond simple deception, creating significant risks for user data and privacy. When users believe they are interacting with a legitimate website, they may unknowingly enter sensitive information such as login credentials, personal data, or financial details. The attack vector is particularly dangerous because it leverages the user's natural trust in browser interface elements rather than attempting to exploit technical vulnerabilities in the browser itself. This makes detection and prevention more challenging for end users who may not recognize the spoofing attempt. Security professionals categorize this as a client-side attack that aligns with ATT&CK technique T1531 for Establishing Persistence and T1566 for Phishing, as it creates conditions for user deception and potential credential theft.
Mitigation strategies for this vulnerability require both immediate remediation and long-term architectural improvements. Browser vendors should implement strict domain validation mechanisms that prevent content loading from different domains while displaying alternative URLs. The fix should include enhanced verification processes that ensure the address bar content accurately reflects the actual content source. Additionally, implementing user education about the risks of address bar spoofing and encouraging verification of URLs through multiple means can help reduce exploitation success rates. Security teams should also consider monitoring for suspicious domain patterns and implementing network-level protections that can detect and block known malicious domains attempting to exploit this vulnerability. The remediation process should include comprehensive testing to ensure that all navigation paths properly validate domain consistency and that users receive appropriate warnings when content does not match displayed URLs.