CVE-2011-1845 in Silverlight
Summary
by MITRE
Multiple memory leaks in the DataGrid control implementation in Microsoft Silverlight 4 before 4.0.60310.0 allow remote attackers to cause a denial of service (memory consumption) via an application involving (1) subscriptions to an INotifyDataErrorInfo.ErrorsChanged event or (2) a TextBlock or TextBox element.
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Analysis
by VulDB Data Team • 11/05/2021
The vulnerability identified as CVE-2011-1845 represents a critical memory management flaw within Microsoft Silverlight 4's DataGrid control implementation. This issue affects versions prior to 4.0.60310.0 and demonstrates a classic memory leak pattern that can be exploited remotely to consume system resources and ultimately lead to denial of service conditions. The vulnerability specifically targets the DataGrid control's handling of event subscriptions and element management, creating persistent memory consumption that degrades system performance over time. Such memory leaks typically occur when application code fails to properly release references to objects that are no longer needed, leading to gradual memory exhaustion that can affect both client applications and server-side processes that utilize Silverlight components.
The technical implementation of this vulnerability manifests through two distinct attack vectors that exploit different aspects of Silverlight's event handling and element management systems. The first vector involves subscriptions to the INotifyDataErrorInfo.ErrorsChanged event, where improper cleanup of event handlers prevents garbage collection of associated objects. The second vector targets TextBlock or TextBox elements within the DataGrid control, where memory allocated for these UI components is not properly released during normal application operations. Both attack paths leverage the fundamental weakness in Silverlight's memory management within the DataGrid control, which fails to properly track and release references to objects that are no longer actively used by the application. This behavior aligns with CWE-401: Improper Release of Memory and represents a failure in proper resource management within the Silverlight runtime environment.
The operational impact of CVE-2011-1845 extends beyond simple resource consumption to potentially compromise entire application availability and system stability. When exploited, these memory leaks can cause progressive memory exhaustion that affects not only the targeted Silverlight application but can also impact the overall system performance by consuming available memory resources that should be allocated to other processes. Attackers can repeatedly trigger these memory leaks through crafted applications or malicious web content, leading to sustained denial of service conditions that may require system restarts to resolve. The vulnerability particularly affects server-side applications that host Silverlight content or client applications that process large amounts of data through DataGrid controls, making it a significant concern for enterprise environments where resource management is critical. This vulnerability maps to ATT&CK technique T1499.004: Endpoint Denial of Service, specifically targeting application stability through resource exhaustion.
Mitigation strategies for CVE-2011-1845 primarily focus on upgrading to the patched version of Microsoft Silverlight 4.0.60310.0 or later, which addresses the memory leak conditions in both event handling and element management. Organizations should implement comprehensive patch management procedures to ensure all Silverlight applications are updated promptly, as the vulnerability affects the core runtime components rather than specific application code. Additionally, developers should implement proper event handler cleanup practices in their applications, explicitly removing subscriptions to INotifyDataErrorInfo.ErrorsChanged events when they are no longer needed. Monitoring application memory usage and implementing resource limits can help detect exploitation attempts before they cause significant system impact. System administrators should also consider implementing network-level controls to restrict access to potentially malicious Silverlight content and maintain regular security assessments to identify applications that may be vulnerable to this class of memory leak attacks. The vulnerability demonstrates the importance of proper memory management in rich internet application frameworks and highlights the need for continuous security monitoring of runtime environments.