CVE-2011-1844 in Silverlight
Summary
by MITRE
Memory leak in Microsoft Silverlight 4 before 4.0.60310.0 allows remote attackers to cause a denial of service (memory consumption) via an application involving a popup control and a custom DependencyProperty property, related to lack of garbage collection.
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Analysis
by VulDB Data Team • 11/05/2021
Microsoft Silverlight 4 suffered from a critical memory leak vulnerability identified as CVE-2011-1844 that affected versions prior to 4.0.60310.0. This flaw specifically manifested when applications utilized popup controls in conjunction with custom DependencyProperty properties, creating a scenario where memory allocated for these components was not properly released back to the system. The vulnerability stems from inadequate garbage collection mechanisms within the Silverlight runtime environment, particularly when handling complex UI elements that involve dependency properties and popup windows. The issue represents a classic memory management flaw that aligns with CWE-401, which addresses improper management of memory allocation and deallocation, and demonstrates how poor resource handling can lead to system instability.
The operational impact of this vulnerability extends beyond simple resource consumption, as it enables remote attackers to systematically exhaust available memory on targeted systems. When exploited, the memory leak causes progressive memory consumption that can eventually lead to application crashes, system slowdowns, or complete denial of service conditions. Attackers can trigger this vulnerability by crafting Silverlight applications that incorporate popup controls with custom dependency properties, making it particularly dangerous in web environments where Silverlight applications are frequently deployed. The vulnerability operates at the runtime level of the Silverlight framework, affecting the underlying memory management subsystem rather than the application logic itself.
This memory leak vulnerability directly relates to the ATT&CK technique T1499.004, which covers network denial of service attacks through resource exhaustion. The flaw enables attackers to consume system resources progressively, ultimately leading to service disruption. The issue is particularly concerning because it affects the core runtime behavior of Silverlight applications, making it difficult to detect and remediate without proper application-level monitoring. The vulnerability's exploitation requires minimal privileges and can be executed through malicious Silverlight content delivered via web browsers, making it an attractive vector for attackers targeting organizations with Silverlight-based applications.
Mitigation strategies for CVE-2011-1844 primarily focus on upgrading to Microsoft Silverlight 4.0.60310.0 or later versions where the memory management issues have been addressed. Organizations should implement comprehensive patch management procedures to ensure all Silverlight applications are updated promptly. Additionally, monitoring memory consumption patterns in Silverlight applications can help detect potential exploitation attempts before they cause significant disruption. System administrators should consider implementing application whitelisting policies to restrict the execution of untrusted Silverlight content, particularly in environments where the vulnerability cannot be immediately patched. The remediation process should also include thorough testing of updated applications to ensure compatibility with the patched Silverlight runtime, as memory management changes may affect existing application behavior.