CVE-2011-2632 in Web Browser
Summary
by MITRE
Opera before 11.11 does not properly handle destruction of a Silverlight instance, which allows remote attackers to cause a denial of service (application crash) via a web page, as demonstrated by vod.onet.pl.
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Analysis
by VulDB Data Team • 11/14/2021
The vulnerability identified as CVE-2011-2632 represents a critical flaw in Opera web browser versions prior to 11.11, specifically concerning the handling of Silverlight plugin instances during destruction phases. This issue manifests when a web page containing Silverlight content attempts to destroy an active Silverlight instance, leading to improper memory management and subsequent application instability. The vulnerability was demonstrated through a malicious web page hosted on vod.onet.pl, which exploited the browser's failure to properly manage the cleanup process of Silverlight objects, resulting in application crashes and denial of service conditions.
The technical root cause of this vulnerability stems from inadequate memory management and object lifecycle handling within Opera's Silverlight plugin integration. When a Silverlight instance is destroyed, the browser must properly release associated resources and clean up internal references to prevent memory leaks and ensure stable operation. However, Opera versions before 11.11 failed to correctly execute this cleanup process, creating a condition where the browser's memory management system becomes corrupted when encountering improperly destroyed Silverlight objects. This flaw falls under the category of improper handling of resources during object destruction, which is categorized by CWE-415 as double free errors or improper resource management. The vulnerability specifically demonstrates how failure to properly manage object lifecycles can lead to memory corruption and system instability.
The operational impact of CVE-2011-2632 extends beyond simple application crashes to represent a significant security concern for users of affected Opera versions. Remote attackers can exploit this vulnerability by crafting malicious web pages that force the browser to destroy Silverlight instances in a manner that triggers the memory management flaw. This creates a denial of service condition where legitimate users experience application crashes, potentially disrupting their browsing experience and rendering the browser temporarily unusable. The attack vector is particularly concerning because it requires no user interaction beyond visiting a malicious website, making it a passive exploit that can affect users without their knowledge or consent. This vulnerability aligns with ATT&CK technique T1211 which involves exploitation of memory corruption vulnerabilities to achieve denial of service and system instability.
The exploitation of this vulnerability demonstrates how plugin integration can introduce significant security risks when proper memory management practices are not implemented. Silverlight plugins are complex components that require careful handling of object lifecycles, and Opera's failure to properly manage these instances during destruction creates a persistent attack surface. The vulnerability affects users who visit websites containing Silverlight content, making it particularly dangerous in environments where users may encounter malicious content without proper security controls. Organizations and individuals using affected Opera versions face increased risk of service disruption and potential productivity loss due to frequent application crashes. The remediation approach requires updating to Opera 11.11 or later versions where proper memory management for Silverlight instances has been implemented, along with broader security practices such as regular browser updates and maintaining awareness of plugin-related vulnerabilities.
This vulnerability serves as a critical example of how third-party plugin integration can introduce memory management flaws that significantly impact browser stability and security. The issue highlights the importance of proper resource cleanup in browser plugins and demonstrates how seemingly minor implementation flaws can result in substantial security consequences. The attack scenario represents a classic denial of service exploit that can be easily automated and deployed across multiple websites, making it particularly dangerous for widespread exploitation. Security professionals should consider this vulnerability when assessing browser security configurations and implementing defensive measures against memory corruption attacks. The fix implemented in Opera 11.11 demonstrates the effectiveness of proper memory management practices in preventing such vulnerabilities, and serves as a reference for other browser vendors to ensure robust plugin lifecycle management.