CVE-2017-2647 in Linux
Summary
by MITRE
The KEYS subsystem in the Linux kernel before 3.18 allows local users to gain privileges or cause a denial of service (NULL pointer dereference and system crash) via vectors involving a NULL value for a certain match field, related to the keyring_search_iterator function in keyring.c.
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Analysis
by VulDB Data Team • 11/24/2022
The vulnerability identified as CVE-2017-2647 resides within the Linux kernel's KEYS subsystem, specifically affecting versions prior to 3.18. This represents a critical security flaw that demonstrates the inherent risks associated with improper input validation in kernel space components. The KEYS subsystem serves as a fundamental mechanism for managing cryptographic keys and credentials within the Linux operating system, making it a prime target for privilege escalation attacks. The vulnerability manifests through a NULL pointer dereference condition that occurs when the keyring_search_iterator function processes certain match fields containing NULL values, creating a scenario where legitimate kernel operations can be exploited to disrupt system stability or gain elevated privileges.
The technical implementation of this vulnerability stems from insufficient validation of match field parameters within the keyring_search_iterator function located in the keyring.c source file. When a local user crafts specific inputs that result in NULL values for critical match fields, the kernel's processing logic fails to properly handle these edge cases, leading to a NULL pointer dereference. This flaw operates at the kernel level, where the absence of proper null checks during keyring search operations creates a condition that can be exploited by malicious users with local access. The vulnerability's classification under CWE-476 indicates a NULL pointer dereference issue, which represents a common yet dangerous class of software defects that can lead to system crashes or unauthorized access. The attack vector specifically requires local user access, as the exploit cannot be executed remotely, but the impact remains severe due to the kernel's privileged execution context.
The operational impact of CVE-2017-2647 extends beyond simple system instability, as it provides attackers with potential paths to privilege escalation or complete system compromise. A successful exploitation can result in either a denial of service condition that crashes the system or allows a local user to gain elevated privileges, potentially enabling access to sensitive system resources and data. The vulnerability's presence in kernel versions prior to 3.18 means that a significant portion of Linux deployments could be affected, particularly in enterprise environments where kernel updates may not be applied immediately. From an attack perspective, this vulnerability aligns with ATT&CK technique T1068 which involves privilege escalation through kernel exploits, and T1499 which encompasses network denial of service attacks that can be initiated from compromised local accounts. The system crash conditions can be particularly disruptive in mission-critical environments where uptime is essential, while the privilege escalation aspect poses a serious threat to data confidentiality and system integrity.
Mitigation strategies for CVE-2017-2647 focus primarily on kernel version updates and system hardening measures. The most effective solution involves upgrading to Linux kernel version 3.18 or later, where the vulnerability has been patched through improved input validation in the keyring_search_iterator function. System administrators should prioritize patch management procedures to ensure timely deployment of kernel updates across all affected systems. Additional defensive measures include implementing strict access controls to limit local user privileges, monitoring for unusual system behavior that might indicate exploitation attempts, and conducting regular security audits of kernel components. The vulnerability's nature suggests that organizations should also consider implementing kernel module signing and secure boot mechanisms to prevent unauthorized modifications to kernel space components. Network segmentation and least privilege principles can help limit the potential impact of successful exploitation by restricting what compromised local accounts can access within the system. Organizations should also maintain detailed system logs and monitoring capabilities to detect any anomalous keyring operations that might indicate attempted exploitation of this vulnerability.