CVE-2011-1344 in Safari
Summary
by MITRE
Use-after-free vulnerability in WebKit, as used in Apple Safari before 5.0.5; iOS before 4.3.2 for iPhone, iPod, and iPad; iOS before 4.2.7 for iPhone 4 (CDMA); and possibly other products allows remote attackers to execute arbitrary code by adding children to a WBR tag and then removing the tag, related to text nodes, as demonstrated by Chaouki Bekrar during a Pwn2Own competition at CanSecWest 2011.
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Analysis
by VulDB Data Team • 12/28/2024
The CVE-2011-1344 vulnerability represents a critical use-after-free flaw in WebKit's HTML parsing and rendering engine that affected Apple Safari and iOS browsers across multiple versions. This vulnerability specifically targeted the handling of text nodes within the WebKit rendering engine, creating a scenario where memory could be accessed after it had been freed, leading to potential arbitrary code execution. The flaw was particularly significant because it could be exploited remotely through web content, making it a serious threat to browser security and user safety.
The technical implementation of this vulnerability involved manipulating the Document Object Model (DOM) structure through specific HTML tag manipulation sequences. Attackers could exploit this by creating a WBR (word break) tag within the HTML document, then adding child elements to this tag before subsequently removing the parent WBR tag. This sequence of operations caused WebKit to maintain references to freed memory locations, particularly in the text node handling code paths. The vulnerability was classified under CWE-416 as a use-after-free condition, which occurs when a program continues to use a pointer after the memory it points to has been freed, creating a classic memory safety issue that can be leveraged for code execution.
The operational impact of this vulnerability was severe as it enabled remote code execution through web-based attacks, potentially allowing attackers to compromise user systems without requiring any local interaction. During the Pwn2Own competition at CanSecWest 2011, security researcher Chaouki Bekrar demonstrated the exploit, showing how the vulnerability could be weaponized to execute arbitrary code on targeted systems. This type of exploit falls under ATT&CK technique T1059.007 for command and scripting interpreter, as it could enable attackers to execute malicious code within the browser environment. The vulnerability affected a wide range of Apple products including Safari versions prior to 5.0.5 and iOS versions before 4.3.2, making it particularly dangerous as it impacted both desktop and mobile platforms.
The exploitation of this vulnerability required careful manipulation of the HTML DOM structure and leveraged the specific memory management behavior of WebKit's text node handling. When the WBR tag was removed from the DOM structure, the associated text nodes would be freed from memory, but references to these memory locations could still persist in the rendering engine's internal data structures. This created a window where attackers could inject malicious data into the freed memory space, potentially leading to code execution when the system attempted to access the corrupted memory locations. The vulnerability highlighted the importance of proper memory management in browser engines and the need for comprehensive input validation in HTML parsing components.
Mitigation strategies for CVE-2011-1344 required immediate software updates from Apple, including Safari 5.0.5 and iOS 4.3.2 updates, which addressed the memory management issues in WebKit's text node handling. Security best practices recommended disabling JavaScript and other potentially dangerous web features when browsing untrusted websites, though this was not a complete solution. The vulnerability underscored the need for robust memory safety mechanisms in browser engines and led to improved testing methodologies for HTML parsing components. Organizations should have implemented patch management processes to ensure timely deployment of security updates, as the vulnerability represented a critical threat that could be exploited by attackers without user interaction. This incident contributed to the broader understanding of memory safety issues in web browsers and influenced subsequent security enhancements in WebKit and other browser engines.