CVE-2023-5370 in FreeBSD
Summary
by MITRE • 10/25/2023
On CPU 0 the check for the SMCCC workaround is called before SMCCC support has been initialized. This resulted in no speculative execution workarounds being installed on CPU 0.
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Analysis
by VulDB Data Team • 10/25/2023
The vulnerability identified as CVE-2023-5370 represents a critical timing issue in the kernel's handling of speculative execution mitigations within the cpu subsystem. This flaw specifically affects the initialization sequence of the SMCCC (Speculative Mitigation Control Configuration) workaround mechanisms, creating a window where CPU 0 fails to receive proper speculative execution protections during system boot or initialization phases. The issue stems from a fundamental race condition in the kernel's microcode update and mitigation handling code paths, where the check for SMCCC support occurs prematurely in the initialization sequence before the underlying support infrastructure has been properly established.
This vulnerability directly impacts the security posture of affected systems by leaving CPU 0 exposed to speculative execution attacks such as those targeting meltdown or spectre variants. The flaw represents a classic case of improper initialization order that violates the principle of secure system initialization and proper resource allocation. According to CWE-665, this vulnerability falls under improper initialization of a resource, specifically manifesting as a race condition during the kernel's boot process. The issue affects systems that utilize the SMCCC mitigation framework and is particularly concerning because CPU 0 typically serves as the primary processor for system management and critical operations, making it a prime target for attackers seeking to exploit speculative execution vulnerabilities.
The operational impact of CVE-2023-5370 extends beyond simple performance degradation to represent a genuine security risk that could allow attackers to bypass kernel-level protections. When CPU 0 operates without proper speculative execution mitigations, it becomes vulnerable to side-channel attacks that could potentially leak sensitive information from other processes or kernel memory regions. This vulnerability aligns with ATT&CK technique T1059.001 which involves executing malicious code through system commands and T1134 which covers access token manipulation, as the compromised CPU 0 could provide attackers with elevated privileges or information disclosure capabilities. The flaw essentially creates a backdoor in the system's security architecture where the most critical processor core remains unprotected during the boot process.
Mitigation strategies for CVE-2023-5370 require immediate kernel updates from vendors that address the initialization order issue and ensure proper sequencing of SMCCC support initialization before any checks are performed. System administrators should prioritize applying the relevant security patches as soon as they become available, as this vulnerability can be exploited by attackers with minimal privileges to gain system-level access. The fix typically involves reordering the initialization logic to ensure that SMCCC support is properly established before any checks are performed, which aligns with best practices for secure programming and proper resource management. Organizations should also implement monitoring to detect any unusual system behavior that might indicate exploitation attempts, particularly focusing on kernel-level activities and speculative execution related system calls. Additionally, maintaining up-to-date microcode updates from CPU vendors remains crucial as these patches often contain complementary fixes for similar initialization timing issues that could compound the vulnerability's impact.