CVE-2016-5267 in Firefox
Summary
by MITRE
Mozilla Firefox before 48.0 on Android allows remote attackers to spoof the address bar via left-to-right characters in conjunction with a right-to-left character set.
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Analysis
by VulDB Data Team • 10/09/2024
This vulnerability in Mozilla Firefox versions prior to 48.0 on Android platforms represents a sophisticated text rendering issue that exploits Unicode bidirectional algorithm inconsistencies to create deceptive user interface elements. The flaw specifically leverages the interaction between left-to-right and right-to-left Unicode character sets to manipulate how URLs are displayed in the browser's address bar, creating a potential vector for phishing attacks and user deception.
The technical implementation of this vulnerability stems from Firefox's handling of bidirectional text processing within the Android version's rendering engine. When malicious actors craft URLs containing specific sequences of right-to-left characters such as Arabic or Hebrew text mixed with left-to-right characters, the browser's text rendering engine fails to properly isolate and display these elements according to Unicode bidirectional rules. This results in the address bar displaying a deceptive representation of the actual URL, where the domain name portion appears to be from a trusted source while the path or scheme may be manipulated to lead users to malicious sites.
From an operational impact perspective, this vulnerability directly violates the fundamental security principle of user interface integrity and trust establishment. Users interacting with the affected Firefox versions may be misled into believing they are visiting legitimate websites when they are actually navigating to malicious domains. The attack vector requires minimal technical expertise from threat actors, as it only requires knowledge of Unicode character sequences rather than complex exploit development. This makes the vulnerability particularly dangerous in mobile environments where users may have reduced ability to manually verify URL authenticity due to smaller screen sizes and touch interface limitations.
The vulnerability aligns with CWE-174, which addresses the weakness of insufficient input validation in bidirectional text handling, and represents a specific implementation gap in Firefox's text rendering engine that fails to properly sanitize Unicode character sequences for display purposes. Security professionals should note the relationship to ATT&CK technique T1059.001, as this vulnerability enables malicious actors to manipulate user trust through interface manipulation rather than direct code execution. The Android-specific nature of this vulnerability also highlights the importance of platform-specific security considerations in mobile browser development, where the interaction between different operating system text rendering engines and browser implementations can create unexpected security gaps.
Mitigation strategies should focus on immediate browser updates to version 48.0 or later, which contain the necessary fixes for proper Unicode bidirectional text handling. Organizations deploying Firefox on Android devices should implement comprehensive security awareness training to help users recognize potential address bar deception, particularly when navigating to unfamiliar domains. Additionally, network-level monitoring should be enhanced to detect unusual URL patterns that might indicate exploitation attempts, while mobile device management solutions should enforce automatic browser update policies to ensure all endpoints receive security patches promptly. The fix implemented by Mozilla specifically addresses the core rendering issue by enforcing stricter Unicode bidirectional algorithm compliance during URL display processing, preventing the manipulation of character ordering that previously enabled the spoofing attack.