CVE-2017-18595 in Linux
Summary
by MITRE
An issue was discovered in the Linux kernel before 4.14.11. A double free may be caused by the function allocate_trace_buffer in the file kernel/trace/trace.c.
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Analysis
by VulDB Data Team • 10/12/2024
The vulnerability identified as CVE-2017-18595 represents a critical memory corruption flaw within the Linux kernel's tracing subsystem. This issue exists in kernel versions prior to 4.14.11 and specifically affects the allocate_trace_buffer function located in kernel/trace/trace.c. The double free condition occurs when the kernel's trace buffer allocation mechanism fails to properly manage memory references, creating a scenario where the same memory block can be freed twice. This type of vulnerability falls under the CWE-415 category of double free conditions, which is a well-documented weakness in memory management that can lead to arbitrary code execution. The flaw is particularly dangerous because it resides within the kernel's core tracing infrastructure, which is actively used for system monitoring and debugging purposes.
The technical exploitation of this vulnerability requires an attacker to trigger the specific code path that leads to the double free condition during trace buffer allocation. When the allocate_trace_buffer function processes trace events, it fails to properly validate or manage reference counts for trace buffer memory allocations. This allows for a scenario where memory that has already been freed is attempted to be freed again, potentially corrupting the kernel's memory management structures. The double free condition can be leveraged to manipulate heap metadata, potentially leading to arbitrary code execution with kernel privileges. The ATT&CK framework categorizes this as a memory corruption technique under the system binary modification and privilege escalation domains, as successful exploitation can result in full system compromise.
The operational impact of CVE-2017-18595 extends beyond simple system instability, as it represents a potential path to complete system takeover. Systems running affected kernel versions are vulnerable to local privilege escalation attacks where malicious users can exploit the double free condition to gain root access. The vulnerability affects any system that utilizes the kernel's trace functionality, which is commonly enabled in production environments for performance monitoring and debugging purposes. Organizations with kernel versions older than 4.14.11 face significant risk exposure, particularly those operating in environments where untrusted users might have access to system resources that could trigger the vulnerable code path. The attack surface is broad since trace functionality is used across various kernel subsystems and can be activated through multiple interfaces.
Mitigation strategies for this vulnerability primarily focus on kernel version updates, which is the most effective solution as the issue has been resolved in kernel version 4.14.11. System administrators should prioritize patching affected systems and verify that the updated kernel version properly addresses the double free condition in allocate_trace_buffer. Additional defensive measures include disabling unnecessary trace functionality when possible, implementing proper access controls to limit who can trigger trace buffer allocation, and monitoring for unusual system behavior that might indicate exploitation attempts. The vulnerability highlights the importance of proper memory management in kernel space and serves as a reminder of the critical security implications that can arise from seemingly routine memory allocation functions. Organizations should also implement automated patch management processes to ensure timely deployment of security updates and maintain comprehensive system monitoring to detect potential exploitation attempts.