CVE-2015-8967 in Linux
Summary
by MITRE • 01/25/2023
arch/arm64/kernel/sys.c in the Linux kernel before 4.0 allows local users to bypass the "strict page permissions" protection mechanism and modify the system-call table, and consequently gain privileges, by leveraging write access.
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Analysis
by VulDB Data Team • 01/25/2023
The vulnerability identified as CVE-2015-8967 represents a critical privilege escalation flaw within the Linux kernel's arm64 architecture implementation. This issue resides in the arch/arm64/kernel/sys.c file and affects kernel versions prior to 4.0, creating a pathway for local attackers to circumvent fundamental security protections that are designed to prevent unauthorized modification of critical system components. The vulnerability specifically targets the "strict page permissions" protection mechanism, which serves as a crucial defense against unauthorized memory modifications that could compromise system integrity.
The technical exploitation of this vulnerability leverages a fundamental flaw in how the kernel handles memory permissions for system call tables. Attackers with local write access can manipulate page permissions to gain the ability to modify the system call table, which serves as the primary interface between user space applications and kernel functions. This manipulation enables attackers to redirect system call execution to malicious code, effectively bypassing the kernel's memory protection mechanisms. The flaw operates at the intersection of memory management and privilege control, where improper permission handling allows for the modification of read-only memory regions that should be protected from user-space modification.
The operational impact of this vulnerability extends beyond simple privilege escalation to encompass complete system compromise. Once an attacker successfully exploits this vulnerability, they gain the ability to execute arbitrary code with kernel-level privileges, enabling them to modify critical system components, install persistent backdoors, or exfiltrate sensitive data. The vulnerability's local nature means that an attacker does not require network access or remote exploitation capabilities, making it particularly dangerous in environments where local access is possible. This characteristic aligns with attack patterns documented in the MITRE ATT&CK framework under privilege escalation techniques, specifically targeting kernel-level vulnerabilities to achieve system compromise.
The root cause of this vulnerability can be traced to inadequate memory permission management within the kernel's arm64 implementation, creating a mismatch between intended security policies and actual implementation. This flaw demonstrates the importance of proper memory protection mechanisms and highlights the critical need for comprehensive testing of privilege control mechanisms in kernel code. The vulnerability's classification aligns with CWE-284, which addresses improper access control, and represents a failure in the kernel's memory management subsystem to properly enforce access restrictions. Organizations affected by this vulnerability should implement immediate mitigations including kernel updates to version 4.0 or later, along with monitoring for suspicious system call table modifications and implementing additional security controls to restrict local user access to minimize potential exploitation scenarios.