CVE-2018-3640 in macOS
Summary
by MITRE
Systems with microprocessors utilizing speculative execution and that perform speculative reads of system registers may allow unauthorized disclosure of system parameters to an attacker with local user access via a side-channel analysis, aka Rogue System Register Read (RSRE), Variant 3a.
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Analysis
by VulDB Data Team • 01/27/2025
The vulnerability identified as CVE-2018-3640 represents a critical side-channel flaw affecting modern microprocessors that employ speculative execution mechanisms. This vulnerability specifically targets systems where processors perform speculative reads of system registers, creating a pathway for unauthorized information disclosure. The issue falls under the broader category of speculative execution side-channel attacks that were widely publicized as part of the Meltdown and Spectre vulnerabilities. Systems affected by this vulnerability include those utilizing Intel processors and potentially other microprocessors implementing similar speculative execution models. The flaw enables local users to perform side-channel analysis that can reveal sensitive system parameters and register contents that should remain protected. This vulnerability is particularly concerning because it operates at the hardware level and can potentially expose confidential information that was never intended to be accessible through normal system operations.
The technical implementation of CVE-2018-3640 exploits the fundamental behavior of modern processors that use speculative execution to improve performance. When a processor speculatively reads system registers during the execution of instructions, it creates observable timing variations or cache behavior changes that can be monitored by malicious code. The vulnerability specifically targets the read operations of system registers that contain sensitive information such as memory management unit (MMU) settings, control registers, and other privileged system data. Attackers can leverage this weakness to infer the contents of these registers through careful analysis of timing differences or cache access patterns. The mechanism works because the speculative execution process leaves observable traces that can be measured and interpreted to reconstruct the values of system parameters. This exploit requires local access and cannot be performed remotely, but it represents a significant threat to systems where local user access might be compromised or where privilege escalation attacks are possible.
The operational impact of CVE-2018-3640 extends beyond simple information disclosure, as it can potentially enable more sophisticated attacks when combined with other vulnerabilities. Systems that rely on processor-based security measures or that implement kernel page table isolation may be particularly vulnerable since the attack can potentially bypass traditional memory protection mechanisms. The vulnerability affects systems where speculative execution is enabled, which includes virtually all modern processors from major manufacturers including Intel, AMD, and ARM. Organizations running critical infrastructure, financial systems, or any environment where system register contents might contain sensitive data are at risk. The attack vector is particularly dangerous because it operates silently and can be performed by any user with local access to the system, making it difficult to detect through standard monitoring procedures. Security researchers have noted that this vulnerability can be used to extract information about memory mappings, privilege levels, and other system parameters that could aid in subsequent attacks or provide insights into system architecture.
Mitigation strategies for CVE-2018-3640 involve both software and hardware approaches that address the underlying speculative execution behavior. System administrators should ensure that operating system patches are applied promptly, as most modern operating systems have implemented mitigations such as kernel page table isolation and retpoline code sequences to prevent the exploitation of speculative execution vulnerabilities. The implementation of microcode updates from processor manufacturers is essential, as these updates often modify the processor's behavior to prevent the specific speculative read operations that enable this attack. Organizations should also consider disabling speculative execution features where possible, though this may result in performance degradation. Network segmentation and access control measures can help limit the potential impact by restricting local access to critical systems. Security monitoring should include detection of unusual timing patterns or cache behavior that might indicate exploitation attempts. The vulnerability aligns with CWE-125, which describes out-of-bounds read conditions, and maps to ATT&CK technique T1059 for execution through local user access, while also relating to T1068 for privilege escalation that could follow successful exploitation. Regular security assessments and vulnerability scanning should be conducted to ensure that systems remain protected against this and related speculative execution attacks.