CVE-2014-4699 in Linux
Summary
by MITRE
The Linux kernel before 3.15.4 on Intel processors does not properly restrict use of a non-canonical value for the saved RIP address in the case of a system call that does not use IRET, which allows local users to leverage a race condition and gain privileges, or cause a denial of service (double fault), via a crafted application that makes ptrace and fork system calls.
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Analysis
by VulDB Data Team • 12/08/2024
The vulnerability described in CVE-2014-4699 represents a critical flaw in the Linux kernel's handling of system calls on Intel processors, specifically affecting versions prior to 3.15.4. This issue stems from improper validation of the saved return instruction pointer (RIP) address during system call execution, creating a pathway for privilege escalation and system instability. The flaw manifests when a system call does not utilize the IRET instruction for return handling, leaving the kernel vulnerable to exploitation through carefully crafted applications that manipulate the instruction pointer in non-canonical address space.
The technical implementation of this vulnerability exploits a race condition within the kernel's privilege management mechanisms. When a process makes ptrace and fork system calls in sequence, the kernel's handling of the saved RIP address becomes susceptible to manipulation. Non-canonical addresses, which are invalid memory addresses that should be rejected by the processor, are not properly restricted in this specific execution path. This allows malicious code to place a non-canonical value in the saved RIP register, effectively creating a situation where the kernel's return mechanism could lead to unpredictable behavior. The vulnerability is particularly dangerous because it leverages the kernel's trust in the instruction pointer value without proper validation checks.
The operational impact of CVE-2014-4699 extends beyond simple privilege escalation to include potential system instability and denial of service conditions. Local attackers with minimal privileges can exploit this vulnerability to gain root access to the system, effectively bypassing all user-level security controls. Additionally, the vulnerability can cause system crashes through double fault conditions when the kernel attempts to return to a non-canonical address, leading to complete system hangs or reboots. This makes the vulnerability particularly dangerous in production environments where system availability is critical, as it can be exploited to perform both persistent privilege escalation attacks and targeted denial of service operations.
This vulnerability maps directly to CWE-122, which describes improper restriction of operations within a recognized security boundary, and aligns with ATT&CK technique T1068, which covers local privilege escalation through kernel exploits. The flaw demonstrates the importance of proper input validation and the necessity of maintaining strict security boundaries even within kernel space. Organizations should immediately apply the kernel patch released in version 3.15.4 to address this vulnerability, as it represents a fundamental flaw in the kernel's privilege management system. System administrators should also implement monitoring for suspicious ptrace and fork activity patterns that might indicate exploitation attempts, while maintaining regular kernel updates to prevent similar vulnerabilities from being exploited in the future.
The broader implications of this vulnerability highlight the complexity of kernel security and the critical importance of proper address validation even in trusted system components. This flaw demonstrates how seemingly minor implementation details in kernel code can create significant security risks, particularly when dealing with processor-specific behavior and privilege boundaries. The vulnerability serves as a reminder of the need for comprehensive testing of edge cases in kernel code and the importance of maintaining up-to-date security patches across all system components to prevent exploitation of such fundamental flaws.