CVE-2015-6115 in .NET Framework
Summary
by MITRE
Microsoft .NET Framework 2.0 SP2, 3.5, and 3.5.1 allows remote attackers to bypass the ASLR protection mechanism via a crafted web site, aka ".NET ASLR Bypass."
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Analysis
by VulDB Data Team • 06/27/2022
The vulnerability identified as CVE-2015-6115 represents a critical security flaw in Microsoft .NET Framework versions 2.0 SP2, 3.5, and 3.5.1 that undermines the operating system's address space layout randomization protection mechanism. This weakness specifically affects the way the .NET Framework handles memory layout during application execution, creating opportunities for attackers to predict memory addresses that would normally be randomized for security purposes. The vulnerability operates through a crafted website that leverages specific behaviors within the .NET runtime environment to expose predictable memory layouts, effectively nullifying the ASLR protection that modern operating systems implement to prevent exploitation of memory corruption vulnerabilities.
The technical flaw stems from insufficient randomization of memory addresses within the .NET Framework's memory management subsystem, particularly affecting how the runtime loads and organizes assemblies and managed code into memory. When a malicious website loads .NET components, the framework fails to properly randomize the base addresses of loaded modules, allowing attackers to determine the memory layout of the target process. This bypass occurs because the .NET Framework's memory allocation routines do not adequately implement the randomization techniques that are expected to be present in modern security architectures, creating predictable memory addresses that attackers can exploit to craft successful exploitation payloads.
The operational impact of this vulnerability extends beyond simple privilege escalation or code execution, as it fundamentally weakens the security posture of systems running affected .NET Framework versions. Attackers can leverage this ASLR bypass to circumvent multiple security mitigations simultaneously, including stack canaries, DEP protection, and other exploit prevention mechanisms that rely on memory layout unpredictability. The vulnerability is particularly dangerous because it affects widely deployed .NET Framework versions that are integral to numerous enterprise applications, web services, and legacy systems, making the attack surface extremely broad. Security researchers have noted that this vulnerability can be exploited in conjunction with other memory corruption flaws to create more sophisticated attack chains that could lead to complete system compromise.
Organizations affected by this vulnerability should immediately apply the relevant security patches provided by Microsoft through their regular update channels, as the fix addresses the core memory randomization issue within the .NET Framework runtime. Additional mitigations include implementing proper network segmentation to limit exposure of affected systems, deploying intrusion detection systems to monitor for suspicious web traffic patterns, and ensuring that all web applications hosted on affected systems are regularly updated and scanned for vulnerabilities. The vulnerability aligns with CWE-1009, which deals with improper handling of security features, and maps to ATT&CK technique T1055.011 for process injection, as attackers can leverage the bypassed ASLR to more effectively execute malicious code within the target environment. Organizations should also consider implementing application whitelisting policies and monitoring for unusual .NET Framework memory access patterns that could indicate exploitation attempts.