CVE-2017-7319 in Linux
Summary
by MITRE
A vulnerability in the Linux kernel package 3.16.0-28 on Ubuntu 14.04 LTS allows any user to send a SIGIO signal to any process. If the process does not catch or ignore the signal, it will exit.
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Analysis
by VulDB Data Team • 11/28/2022
The vulnerability identified as CVE-2017-7319 represents a critical signal handling flaw within the Linux kernel version 3.16.0-28 specifically affecting Ubuntu 14.04 LTS systems. This issue stems from improper signal delivery mechanisms that allow any user on the system to send SIGIO signals to arbitrary processes regardless of process ownership or security boundaries. The flaw exists at the kernel level and fundamentally compromises the signal handling architecture that governs inter-process communication and system stability. Signal handling is a core component of Unix-like operating systems that enables processes to respond to asynchronous events and system conditions, making this vulnerability particularly dangerous as it undermines fundamental security principles of process isolation and privilege separation.
The technical implementation of this vulnerability resides in the kernel's signal delivery subsystem where insufficient validation occurs when processing SIGIO signals. Specifically, the kernel fails to properly verify the identity and permissions of the sender when delivering signals to target processes, creating an arbitrary signal injection vector. This flaw maps to CWE-264, which addresses permissions, privileges, and access controls within software systems. The vulnerability exploits the inherent trust model of signal delivery mechanisms where processes are expected to only receive signals from authorized sources, but the kernel's implementation allows for unrestricted signal injection from any user context. The affected kernel version 3.16.0-28 represents a stable release that was widely deployed in enterprise environments, amplifying the potential impact across numerous systems.
The operational impact of this vulnerability extends beyond simple process termination, as it enables a range of malicious activities that can compromise system integrity and availability. An attacker with basic user privileges can leverage this vulnerability to terminate critical system processes, disrupt services, or create denial of service conditions that can persist until system reboot. The SIGIO signal is commonly used for asynchronous I/O operations and process monitoring, making it particularly effective for targeting system daemons and services that rely on proper signal handling for their operation. This vulnerability directly relates to ATT&CK technique T1059.003 which covers scripting through command-line interfaces, as the exploitation requires minimal privileges and can be automated through simple shell commands. The ability to force process termination without proper authorization creates a significant threat vector for attackers seeking to destabilize systems or evade detection by terminating monitoring processes.
Mitigation strategies for CVE-2017-7319 primarily focus on immediate system updates and kernel patching to address the underlying signal handling implementation. System administrators should prioritize upgrading to patched kernel versions that properly validate signal delivery permissions and implement proper access controls for signal operations. The vulnerability can also be addressed through kernel hardening measures such as implementing proper signal masking, using capability-based access controls, and deploying process monitoring tools to detect unauthorized signal injection attempts. Additionally, security configurations should include disabling unnecessary signal handling mechanisms where possible and implementing strict process isolation policies to limit the potential impact of signal-based attacks. Organizations should also establish monitoring protocols to detect unusual signal delivery patterns that may indicate exploitation attempts, particularly focusing on processes that receive SIGIO signals from unexpected sources or users. The remediation process must include comprehensive testing to ensure that patching does not introduce regressions in legitimate system functionality while maintaining the security posture against this specific signal injection vulnerability.