CVE-2011-0992 in Moonlight
Summary
by MITRE
Use-after-free vulnerability in Mono, when Moonlight 2.x before 2.4.1 or 3.x before 3.99.3 is used, allows remote attackers to cause a denial of service (plugin crash) or obtain sensitive information via vectors related to member data in a resurrected MonoThread instance.
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Analysis
by VulDB Data Team • 11/02/2021
The CVE-2011-0992 vulnerability represents a critical use-after-free condition within the Mono runtime environment that specifically affects Moonlight 2.x versions prior to 2.4.1 and Moonlight 3.x versions prior to 3.99.3. This flaw exists within the handling of member data within resurrected MonoThread instances, creating a scenario where memory that has been freed is still accessed by subsequent operations. The vulnerability stems from improper memory management practices within the Mono runtime's threading model, where thread resurrection mechanisms fail to properly invalidate references to previously freed memory structures. This issue demonstrates a classic software security weakness that aligns with CWE-416, which specifically addresses use-after-free vulnerabilities in memory management operations. The vulnerability is particularly concerning because it occurs within the core runtime components that manage application execution flow and thread lifecycle management.
The technical exploitation of this vulnerability occurs when a malicious attacker crafts specific input that triggers the resurrection of a MonoThread instance while maintaining references to previously freed memory segments. During the resurrection process, the runtime attempts to access member data that has already been deallocated from memory, causing either a segmentation fault that results in plugin crash or potentially allowing memory corruption that could lead to information disclosure. The attack vector leverages the timing and state management aspects of thread resurrection, where the Mono runtime fails to properly track memory references across thread lifecycle transitions. This particular flaw demonstrates the complexity of managing memory in managed runtime environments where garbage collection and thread management interact in potentially unpredictable ways, creating opportunities for attackers to exploit the temporal gaps in memory state management. The vulnerability is categorized under the broader ATT&CK technique T1059 which covers command and scripting interpreter usage, as the exploitation could potentially lead to more sophisticated attacks through memory corruption.
The operational impact of CVE-2011-0992 extends beyond simple denial of service conditions to potentially enable more serious security compromises within affected systems. When the vulnerability results in plugin crashes, it can disrupt legitimate user sessions and service availability, particularly in web environments where Moonlight plugins are commonly used for rich media content delivery. The information disclosure aspect poses a more significant threat, as attackers could potentially extract sensitive data from memory locations that should no longer be accessible, potentially including authentication tokens, user credentials, or application state information. Organizations running affected versions of Moonlight are particularly vulnerable in environments where the plugin is used for business-critical applications, as the instability could lead to data loss or service interruptions. The vulnerability affects not only the immediate user experience but also creates potential entry points for attackers seeking to escalate privileges or conduct further reconnaissance within the compromised system. This issue highlights the importance of proper memory management in managed runtime environments and the need for thorough testing of thread lifecycle management code. The vulnerability's impact is amplified in web browser environments where plugin security is paramount, as it could potentially be exploited to bypass security boundaries and access protected resources. Organizations should prioritize patching affected systems and implementing additional monitoring to detect potential exploitation attempts, particularly in environments where Moonlight plugins are actively used for content delivery.