CVE-2012-6689 in Linux
Summary
by MITRE • 01/25/2023
The netlink_sendmsg function in net/netlink/af_netlink.c in the Linux kernel before 3.5.5 does not validate the dst_pid field, which allows local users to have an unspecified impact by spoofing Netlink messages.
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Analysis
by VulDB Data Team • 01/25/2023
The vulnerability identified as CVE-2012-6689 resides within the Linux kernel's netlink subsystem, specifically in the netlink_sendmsg function located in net/netlink/af_netlink.c. This flaw represents a critical security weakness that affects Linux kernel versions prior to 3.5.5, where the kernel fails to properly validate the dst_pid field during netlink message transmission. The netlink protocol serves as a bidirectional communication channel between kernel space and user space processes, making it a fundamental component for system administration and network management operations. The absence of validation for the destination process identifier field creates a pathway for malicious local users to manipulate netlink message routing and potentially bypass security controls.
The technical implementation of this vulnerability stems from the kernel's failure to perform proper input validation on the dst_pid parameter within the netlink_sendmsg function. When a user-space process attempts to send a netlink message, the kernel should verify that the destination process identifier corresponds to a legitimate target within the system. However, due to the missing validation check, an attacker can craft malicious netlink messages with arbitrary dst_pid values that may redirect messages to unintended recipients or even to kernel space itself. This validation gap allows for potential privilege escalation scenarios where local users can manipulate the kernel's message routing behavior to achieve unauthorized access or system compromise.
The operational impact of this vulnerability extends beyond simple message spoofing, as it enables local users to potentially manipulate kernel behavior through carefully crafted netlink communications. Attackers can exploit this weakness to send messages that appear to originate from legitimate kernel processes, thereby bypassing security mechanisms that rely on proper process identification. The unspecified impact mentioned in the CVE description reflects the broad range of potential consequences, including but not limited to privilege escalation, denial of service conditions, and information disclosure. The vulnerability is particularly concerning because it operates at the kernel level, meaning that successful exploitation could result in complete system compromise without requiring elevated privileges beyond local access.
Mitigation strategies for CVE-2012-6689 primarily focus on upgrading to Linux kernel versions 3.5.5 or later, where the validation issue has been addressed through proper input validation of the dst_pid field. System administrators should prioritize kernel updates as part of their regular security maintenance procedures to protect against this and similar vulnerabilities. Additional protective measures include implementing proper access controls and monitoring for anomalous netlink message patterns that could indicate exploitation attempts. The vulnerability aligns with CWE-20, which describes improper input validation, and can be mapped to ATT&CK technique T1068, which covers local privilege escalation through kernel vulnerabilities. Organizations should also consider implementing network segmentation and process monitoring to detect and prevent potential exploitation attempts targeting the netlink subsystem.
This vulnerability demonstrates the critical importance of proper input validation in kernel space operations, where even seemingly minor oversights can create significant security risks. The netlink protocol's design as a communication bridge between kernel and user space makes it particularly sensitive to validation failures, as improper handling can lead to arbitrary code execution or privilege escalation within the kernel context. Security practitioners should recognize that vulnerabilities in core kernel subsystems like netlink represent high-risk targets for exploitation, as they can provide attackers with direct pathways to system compromise. The fix implemented in kernel versions 3.5.5 and later serves as a reminder of the essential nature of thorough code review and validation processes in security-critical components of operating system kernels.