CVE-2018-15594 in Linux
Summary
by MITRE
arch/x86/kernel/paravirt.c in the Linux kernel before 4.18.1 mishandles certain indirect calls, which makes it easier for attackers to conduct Spectre-v2 attacks against paravirtual guests.
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Analysis
by VulDB Data Team • 05/02/2023
The vulnerability identified as CVE-2018-15594 resides within the Linux kernel's paravirtualization implementation, specifically in the arch/x86/kernel/paravirt.c file. This flaw affects versions prior to 4.18.1 and represents a critical security issue that significantly weakens the kernel's protection against side-channel attacks. The vulnerability stems from improper handling of indirect calls within the paravirtualization framework, creating exploitable conditions that attackers can leverage to bypass security mitigations. Paravirtualized environments, which are commonly used in cloud computing and virtual machine deployments, become particularly susceptible to this weakness as they rely heavily on the kernel's virtualization layer for secure operation.
The technical flaw manifests in the kernel's approach to managing indirect function calls within the paravirtualization code path. When the kernel processes these indirect calls, it fails to properly account for the potential for speculative execution to occur across virtualization boundaries. This mismanagement creates a pathway for attackers to exploit the Spectre-v2 variant of speculative execution attacks, which targets indirect branch prediction mechanisms. The vulnerability essentially allows malicious actors to manipulate the kernel's indirect call handling in a way that exposes sensitive information through cache timing side channels. This particular weakness is especially dangerous because it operates at the kernel level and affects the core virtualization infrastructure that many cloud providers and enterprise environments depend upon.
The operational impact of CVE-2018-15594 extends beyond simple privilege escalation or information disclosure. Organizations running paravirtualized guests are at heightened risk of exposure to sophisticated attacks that can extract confidential data from memory regions that should remain protected. The vulnerability particularly affects cloud environments where multiple tenants share the same physical hardware, as attackers could potentially exploit this weakness to access data belonging to other virtual machines. This scenario represents a significant threat to multi-tenant cloud infrastructures and can compromise the fundamental security assumptions that underpin virtualized computing environments. The vulnerability's impact is amplified by the fact that it affects the underlying kernel mechanisms that provide security guarantees to virtualized systems, making it a critical concern for any organization relying on paravirtualization technologies.
Mitigation strategies for CVE-2018-15594 require immediate kernel updates to version 4.18.1 or later, which contain the necessary patches to address the improper indirect call handling. Organizations should also implement additional security controls including disabling unnecessary paravirtualization features when possible, applying microcode updates from hardware vendors, and monitoring for suspicious activity patterns that might indicate exploitation attempts. The fix addresses the root cause by properly managing the speculative execution behavior during indirect calls and ensuring that virtualization boundaries remain intact. Security teams should conduct comprehensive assessments of their virtualized environments to identify all systems running affected kernel versions and prioritize remediation efforts accordingly. This vulnerability serves as a reminder of the critical importance of keeping kernel components up to date and maintaining robust security practices in virtualized environments where the attack surface can be significantly expanded by kernel-level weaknesses. The issue aligns with CWE-119 which addresses memory safety issues, and relates to ATT&CK technique T1059.001 for execution through kernel modules and T1059.007 for execution through virtualization software.