CVE-2006-3513 in Internet Explorer
Summary
by MITRE
danim.dll in Microsoft Internet Explorer 6 allows remote attackers to cause a denial of service (application crash) by accessing the Data property of a DirectAnimation DAUserData object before it is initialized, which triggers a NULL pointer dereference.
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Analysis
by VulDB Data Team • 04/07/2017
The vulnerability identified as CVE-2006-3513 represents a critical denial of service flaw within Microsoft Internet Explorer 6's handling of DirectAnimation components. This issue specifically affects the danimdll library which is responsible for processing DirectAnimation objects within the browser environment. The vulnerability stems from improper initialization handling of DAUserData objects, creating a scenario where application stability is compromised through maliciously crafted web content. The flaw exists in the browser's object model handling where the Data property of DirectAnimation objects is accessed without proper validation of the object's initialization state, leading to unpredictable behavior and system instability.
The technical mechanism behind this vulnerability operates through a NULL pointer dereference condition that occurs when the Data property of a DAUserData object is accessed before the object has been properly initialized. This type of error represents a classic software engineering flaw where memory management and object lifecycle handling are not properly enforced. When Internet Explorer attempts to access the Data property of an uninitialized DirectAnimation object, the application encounters a NULL reference that cannot be properly handled, resulting in an application crash and complete denial of service for the affected user. The vulnerability is particularly concerning because it can be triggered through standard web browsing activities without requiring any special privileges or user interaction beyond visiting a malicious webpage.
From an operational impact perspective, this vulnerability presents a significant risk to enterprise environments where Internet Explorer 6 remains in use, as it can be exploited by remote attackers to disrupt normal browser operations and potentially affect productivity. The denial of service condition affects the entire browser application, making it impossible for users to continue browsing until the application is manually restarted. This vulnerability also demonstrates the broader security implications of improper object initialization in rich client applications, where the complexity of object models can create numerous potential attack vectors. The flaw aligns with CWE-476 which specifically addresses NULL pointer dereference conditions, and represents a typical example of how insufficient input validation can lead to application instability and potential exploitation.
The exploitation of this vulnerability requires minimal technical skill from attackers, as it can be triggered through standard web content without requiring any specialized tools or knowledge of advanced exploitation techniques. This makes the vulnerability particularly dangerous in environments where users may inadvertently visit malicious websites or where social engineering attacks are employed to deliver the exploit. The vulnerability also highlights the importance of proper software quality assurance and testing practices, particularly around object initialization and memory management in complex software applications. Organizations using Internet Explorer 6 should consider immediate mitigation strategies including browser updates, security patches, or deployment of additional protective measures to prevent exploitation of this vulnerability.
Security professionals should note that this vulnerability exemplifies the types of issues that became more prevalent as web browsers evolved to support increasingly complex multimedia and animation capabilities. The DirectAnimation technology, while providing enhanced web experiences, introduced additional attack surface areas that were not adequately protected against improper usage patterns. This vulnerability also demonstrates the need for robust error handling and defensive programming practices in browser implementations, particularly when dealing with complex object models and asynchronous operations that may not complete initialization before being accessed. The flaw serves as a reminder of the critical importance of proper software lifecycle management and the potential consequences of inadequate testing for edge cases and error conditions in widely deployed applications.