CVE-2011-3663 in Firefox
Summary
by MITRE
Mozilla Firefox 4.x through 8.0, Thunderbird 5.0 through 8.0, and SeaMonkey before 2.6 allow remote attackers to capture keystrokes entered on a web page, even when JavaScript is disabled, by using SVG animation accessKey events within that web page.
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Analysis
by VulDB Data Team • 03/20/2021
This vulnerability represents a critical security flaw in Mozilla Firefox versions 4.0 through 8.0, Thunderbird versions 5.0 through 8.0, and SeaMonkey versions prior to 2.6 that allows remote attackers to capture keystrokes entered on web pages even when JavaScript is disabled. The vulnerability stems from improper handling of SVG animation accessKey events that can be manipulated to capture keyboard input without user consent. The technical implementation involves the exploitation of SVG (Scalable Vector Graphics) elements that contain animation attributes which can trigger accessKey events, enabling attackers to capture keystrokes from users who believe they are protected by JavaScript disablement. This flaw operates at the browser rendering engine level, specifically affecting how the browser processes SVG elements and handles keyboard event propagation within web page contexts. The vulnerability is categorized under CWE-254 as it represents a weakness in the security model of the browser, specifically in how it handles keyboard input in SVG contexts. From an operational perspective, this vulnerability enables attackers to perform keystroke logging attacks that can capture sensitive information such as passwords, credit card numbers, and personal identification details entered into web forms. The attack vector is particularly concerning because it bypasses common security measures that users employ to protect themselves, including disabling JavaScript, which is a standard defense mechanism against many web-based attacks. The vulnerability is also aligned with ATT&CK technique T1056.001 which involves credential injection through input capture mechanisms. Attackers can leverage this vulnerability by crafting malicious web pages that contain SVG elements with animation attributes that trigger accessKey events. When users interact with these pages, the malicious code can capture keystrokes without requiring JavaScript execution, as the vulnerability occurs at the SVG processing level within the browser engine itself. This creates a sophisticated attack surface that can be exploited across multiple Mozilla-based applications, extending the impact beyond just web browsers to email clients that share the same underlying rendering engine. The vulnerability represents a fundamental flaw in the browser's security model and can be exploited in various scenarios including phishing attacks, credential harvesting, and data exfiltration operations. The severity is compounded by the fact that users may not be aware they are being targeted, as the attack occurs silently in the background without obvious indicators. Organizations and users should be particularly concerned about this vulnerability as it undermines the basic security assumptions that users make about their browser security settings. The attack requires no special privileges or user interaction beyond visiting a malicious website, making it particularly dangerous in phishing campaigns and targeted attacks. Mitigation efforts should focus on immediate patching of affected versions, implementing network-level protections such as content filtering, and educating users about the importance of keeping their browser software up to date. The vulnerability demonstrates the complexity of modern browser security and the importance of comprehensive testing of all rendering engine components, particularly those that handle multimedia and vector graphics elements. Security teams should also consider implementing browser hardening measures that limit the execution of potentially dangerous SVG elements and monitor for unusual keyboard event patterns that might indicate exploitation attempts.