CVE-2016-1940 in Firefox
Summary
by MITRE
Mozilla Firefox before 44.0 on Android allows remote attackers to spoof the address bar via a data: URL that is mishandled during (1) shortcut opening or (2) BOOKMARK intent processing.
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Analysis
by VulDB Data Team • 07/06/2022
This vulnerability resides in the Mozilla Firefox browser implementation for Android devices, specifically affecting versions prior to 44.0. The security flaw manifests through improper handling of data: URLs during two distinct operational phases of the browser's address bar functionality. The vulnerability enables remote attackers to craft malicious data: URLs that can manipulate the browser's display behavior, creating deceptive user interfaces that appear to show legitimate web addresses while actually presenting malicious content. This represents a significant user interface deception attack vector that undermines the fundamental security principle of address bar integrity and user trust in the browser's navigation indicators.
The technical implementation flaw occurs within Firefox's Android-specific code handling for shortcut opening and BOOKMARK intent processing. During these operations, the browser fails to properly validate or sanitize data: URLs that contain embedded content or formatting instructions. This improper URL handling allows attackers to inject content that modifies how the address bar displays information to users. The vulnerability specifically affects the browser's parsing and rendering logic for data: URLs, where the application does not adequately distinguish between legitimate address bar content and potentially malicious spoofing attempts. This weakness creates a path for attackers to manipulate the user's perception of their current browsing location through carefully crafted URL schemes that exploit the browser's trust in its own display mechanisms.
The operational impact of this vulnerability extends beyond simple phishing attacks to encompass a broader range of social engineering and user deception scenarios. Attackers can exploit this flaw to make users believe they are visiting legitimate websites while actually navigating to malicious destinations. This spoofing capability undermines the browser's security model by allowing attackers to bypass user verification mechanisms that rely on address bar trust. The vulnerability affects Android users specifically, making it particularly concerning given the mobile browsing landscape and the increased exposure to malicious content through mobile applications. Users may be tricked into entering sensitive information or downloading malware, as the deceptive address bar display reduces their ability to accurately identify the true destination of their navigation requests.
Mitigation strategies for this vulnerability require immediate browser updates to version 44.0 or later, where Mozilla has implemented proper URL validation and sanitization for data: URLs during shortcut and bookmark processing. System administrators and security professionals should ensure all Firefox installations on Android devices are updated to the patched version to prevent exploitation. Additionally, users should be educated about the importance of verifying website addresses and not relying solely on address bar appearance for security assessment. The vulnerability demonstrates the critical importance of proper input validation and URL handling in web browsers, particularly when dealing with privileged operations like address bar display. Security teams should implement monitoring for suspicious URL patterns and consider deploying network-level controls to detect and block potentially malicious data: URL traffic. This vulnerability aligns with CWE-79 and CWE-1021 categories related to improper input validation and user interface security, and represents a technique that could be classified under ATT&CK tactics involving defense evasion and credential access through social engineering. Organizations should also consider implementing browser security policies that restrict data: URL handling or require additional verification steps for bookmark operations to provide layered protection against similar spoofing attacks.