CVE-2017-7759 in Firefox
Summary
by MITRE
Android intent URLs given to Firefox for Android can be used to navigate from HTTP or HTTPS URLs to local "file:" URLs, allowing for the reading of local data through a violation of same-origin policy. Note: This attack only affects Firefox for Android. Other operating systems are not affected. This vulnerability affects Firefox < 54.
VulDB is the best source for vulnerability data and more expert information about this specific topic.
Analysis
by VulDB Data Team • 12/28/2020
This vulnerability represents a critical cross-origin access flaw in Firefox for Android that exploits the browser's handling of Android intent URLs. The issue arises from how Firefox for Android processes intent URLs that are designed to launch applications on Android devices, creating an unexpected pathway for privilege escalation. When users navigate from standard HTTP or HTTPS web pages to local file URLs through these intent mechanisms, the browser fails to properly enforce same-origin policy restrictions that normally prevent such cross-domain access.
The technical implementation of this vulnerability stems from Firefox for Android's incomplete validation of intent URL schemes when transitioning between web content and local system resources. Specifically, the browser's intent handling mechanism does not adequately distinguish between trusted web origins and local file system access points, allowing attackers to craft malicious URLs that leverage the Android intent system to access local file resources. This flaw operates at the intersection of mobile browser security and Android application framework security, where the browser's trust model becomes compromised when processing certain URL formats.
The operational impact of this vulnerability is significant for users of Firefox for Android versions prior to 54, as it enables arbitrary file reading capabilities that could expose sensitive local data. Attackers can potentially access files stored on the device's file system, including personal documents, application data, and potentially system files that should remain protected from web-based access. This represents a fundamental violation of the browser's security model where web content gains unauthorized access to local resources, potentially leading to data exfiltration and privacy breaches. The vulnerability specifically targets the Android platform's unique intent system while maintaining compatibility with standard web protocols.
This issue aligns with CWE-200 (Information Exposure) and CWE-284 (Improper Access Control) classifications, demonstrating how improper handling of cross-platform integration mechanisms can create security holes in mobile browsers. The vulnerability also maps to ATT&CK technique T1059.007 (Command and Scripting Interpreter: JavaScript) and T1071.004 (Application Layer Protocol: DNS) in contexts where attackers leverage browser-based attacks to access local resources. The attack vector requires user interaction through malicious web content, making it particularly concerning for phishing campaigns and targeted attacks. Organizations should ensure all Firefox for Android installations are updated to version 54 or later to mitigate this risk, as the vulnerability specifically affects only the Android mobile browser variant and does not impact other operating systems or desktop versions of Firefox.