CVE-2013-6791 in Enhanced Mitigation Experience Toolkit EMET
Summary
by MITRE
Microsoft Enhanced Mitigation Experience Toolkit (EMET) before 4.0 uses predictable addresses for hooked functions, which makes it easier for context-dependent attackers to defeat the ASLR protection mechanism via a return-oriented programming (ROP) attack.
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Analysis
by VulDB Data Team • 12/23/2024
The vulnerability identified as CVE-2013-6791 affects Microsoft Enhanced Mitigation Experience Toolkit version 3.0 and earlier, representing a critical weakness in the implementation of address space layout randomization protection mechanisms. This flaw specifically impacts the toolkit's approach to function hooking, where the predictable memory addresses used for hooked functions create exploitable patterns that adversaries can leverage to bypass security protections. The issue stems from the toolkit's failure to properly randomize or obscure the memory locations of hooked functions, which directly undermines the fundamental purpose of ASLR (Address Space Layout Randomization) in protecting against memory corruption attacks.
The technical flaw manifests through the predictable addressing scheme employed by EMET version 3.0 and earlier, where hooked functions are placed at consistent memory locations across different system instances or executions. This predictability enables attackers to craft return-oriented programming attacks with precision, as they can reliably locate the target functions in memory without requiring extensive enumeration or exploitation techniques. The vulnerability operates at the intersection of software security mechanisms, where the mitigation toolkit itself becomes a vector for exploitation rather than a protective barrier. This represents a classic case of security through obscurity failing when predictable patterns are introduced into the system's memory management.
The operational impact of this vulnerability extends beyond simple privilege escalation or code execution capabilities, as it fundamentally compromises the security posture of systems relying on EMET for protection. Attackers can leverage the predictable function addresses to bypass multiple security controls simultaneously, including ASLR, DEP (Data Execution Prevention), and stack canaries, through carefully constructed ROP chains that exploit these known memory locations. The vulnerability affects the broader security ecosystem by demonstrating how well-intentioned security tools can introduce new attack surfaces when their implementation lacks proper randomness or entropy in critical memory allocation patterns. This weakness particularly impacts enterprise environments where EMET is deployed as part of comprehensive security strategies, potentially allowing attackers to gain unauthorized access to sensitive systems.
Mitigation strategies for this vulnerability require immediate deployment of EMET version 4.0 or later, which addresses the predictable addressing issue through improved randomization techniques for hooked function placement. Organizations should conduct comprehensive security assessments to identify systems running vulnerable EMET versions and ensure all endpoints are updated to the latest toolkit release. The fix implemented in EMET 4.0 addresses the underlying flaw by introducing proper entropy into the function hooking mechanism, making memory addresses unpredictable and significantly reducing the effectiveness of ROP-based attacks. Security teams should also implement additional monitoring and detection capabilities to identify potential exploitation attempts targeting this specific vulnerability, while maintaining awareness of related ATT&CK techniques such as T1059.007 for PowerShell-based exploitation and T1070.004 for bypassing application control measures. The vulnerability aligns with CWE-1004 which addresses insecure coding practices related to predictable memory addresses in security-critical applications, and demonstrates the importance of proper randomization in security implementation as outlined in various NIST cybersecurity guidelines.