CVE-2012-6657 in Linux
Summary
by MITRE
The sock_setsockopt function in net/core/sock.c in the Linux kernel before 3.5.7 does not ensure that a keepalive action is associated with a stream socket, which allows local users to cause a denial of service (system crash) by leveraging the ability to create a raw socket.
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Analysis
by VulDB Data Team • 02/16/2022
The vulnerability described in CVE-2012-6657 represents a critical flaw in the Linux kernel's socket implementation that enables local privilege escalation and system instability. This issue resides within the sock_setsockopt function located in net/core/sock.c, which is responsible for setting socket options and managing socket behavior. The vulnerability specifically affects Linux kernel versions prior to 3.5.7, making it a significant concern for systems running older kernel versions. The flaw manifests when the kernel fails to properly validate socket types during keepalive configuration operations, creating an exploitable condition that can be leveraged by local attackers to crash the system.
The technical nature of this vulnerability stems from improper socket type validation within the kernel's networking stack. When a local user creates a raw socket and attempts to configure keepalive parameters, the sock_setsockopt function does not adequately verify that the keepalive action is being applied to a stream socket type. This validation gap allows attackers to bypass normal socket type restrictions and potentially trigger kernel memory corruption or invalid memory access patterns. The flaw operates at the kernel level, making it particularly dangerous as it can be exploited without requiring network access or remote connectivity. The vulnerability demonstrates a classic case of insufficient input validation and type checking, which falls under the CWE-248 category of "Uncaught Exception" and represents a failure in proper error handling within kernel space operations.
The operational impact of this vulnerability extends beyond simple denial of service to potentially enable more sophisticated attacks. Local users can leverage this flaw to cause system crashes, leading to complete system unavailability and potential data loss. The attack vector is particularly concerning because it requires minimal privileges and can be executed from within the system itself, making it difficult to detect and prevent through traditional network monitoring. The vulnerability's exploitation can result in system instability that may persist until manual reboot occurs, effectively creating a persistent denial of service condition. From an attacker's perspective, this represents a valuable primitive for gaining system control, as system crashes can be used to disrupt services or potentially create conditions for further exploitation.
Mitigation strategies for CVE-2012-6657 focus primarily on kernel version upgrades to 3.5.7 or later, which contain the necessary patches to address the socket type validation issue. System administrators should prioritize updating kernel versions across all affected systems, particularly those running older Linux distributions that may not have received timely security updates. Additionally, implementing proper access controls and monitoring for unusual socket creation patterns can help detect potential exploitation attempts. The vulnerability aligns with ATT&CK technique T1068 which covers "Local Privilege Escalation" and demonstrates how kernel-level flaws can be exploited to gain system control. Organizations should also consider implementing kernel hardening measures such as disabling unnecessary socket types and restricting raw socket creation where possible. Regular security audits and vulnerability assessments should include checks for outdated kernel versions to prevent exploitation of similar historical vulnerabilities. The fix implemented in kernel version 3.5.7 specifically addresses the missing validation logic in sock_setsockopt, ensuring that keepalive operations are properly restricted to appropriate socket types and preventing the invalid memory access patterns that led to system crashes.