CVE-2017-2618 in Linux
Summary
by MITRE
A flaw was found in the Linux kernel's handling of clearing SELinux attributes on /proc/pid/attr files before 4.9.10. An empty (null) write to this file can crash the system by causing the system to attempt to access unmapped kernel memory.
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Analysis
by VulDB Data Team • 04/27/2023
The vulnerability described in CVE-2017-2618 represents a critical kernel-level flaw in the Linux operating system's security module implementation. This issue specifically affects the SELinux (Security-Enhanced Linux) subsystem's handling of process attribute files within the /proc filesystem. The vulnerability exists in kernel versions prior to 4.9.10 and demonstrates a fundamental failure in memory management during attribute clearing operations. The flaw manifests when an empty or null write operation is performed on /proc/pid/attr files, which are used to manage security contexts for running processes. This particular vulnerability falls under the category of improper handling of empty or null inputs, which is categorized as CWE-457 in the CWE database.
The technical exploitation of this vulnerability occurs through a specific race condition in the kernel's SELinux attribute clearing mechanism. When a process attempts to clear SELinux attributes by writing to the /proc/pid/attr file, the kernel fails to properly validate the input data before proceeding with memory operations. The empty write operation triggers an uninitialized memory access pattern that leads to kernel memory corruption. This type of vulnerability is particularly dangerous because it operates at the kernel level where memory access violations can result in complete system compromise rather than just application-level crashes. The flaw directly relates to the ATT&CK technique T1068 which involves exploiting vulnerabilities in kernel-mode software to gain elevated privileges.
The operational impact of CVE-2017-2618 extends beyond simple system crashes to potentially enable privilege escalation attacks. An attacker who can successfully exploit this vulnerability can cause a denial of service by crashing the system or, in more sophisticated scenarios, may be able to leverage the memory corruption to execute arbitrary code with kernel privileges. The vulnerability affects systems running Linux kernel versions before 4.9.10, which includes many enterprise and server deployments. Organizations using affected kernel versions face significant risk as this flaw can be exploited remotely or locally depending on system configuration. The vulnerability also impacts systems that utilize SELinux policies extensively, making it particularly concerning for security-sensitive environments that rely on mandatory access controls.
Mitigation strategies for CVE-2017-2618 primarily focus on kernel version updates and system hardening measures. The most effective solution is upgrading to Linux kernel version 4.9.10 or later, where the vulnerability has been patched through proper input validation and memory management improvements. System administrators should also implement monitoring for suspicious write operations to /proc/pid/attr files and consider disabling unnecessary SELinux functionality when not required. Additional defensive measures include implementing proper kernel lockdown mechanisms, restricting write permissions to sensitive proc filesystem entries, and deploying intrusion detection systems that can identify anomalous behavior patterns associated with this vulnerability. The patch for this vulnerability specifically addresses the improper handling of null writes by ensuring that kernel memory is properly initialized before access operations, which aligns with security best practices for preventing uninitialized memory access patterns.