CVE-2014-4943 in Linux
Summary
by MITRE
The PPPoL2TP feature in net/l2tp/l2tp_ppp.c in the Linux kernel through 3.15.6 allows local users to gain privileges by leveraging data-structure differences between an l2tp socket and an inet socket.
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Analysis
by VulDB Data Team • 11/20/2024
The vulnerability identified as CVE-2014-4943 resides within the Linux kernel's implementation of the Point-to-Point Protocol over Layer 2 Tunneling Protocol version 2 (PPPoL2TP) functionality. This flaw exists in the net/l2tp/l2tp_ppp.c file and affects kernel versions through 3.15.6, representing a significant local privilege escalation vector that exploits fundamental differences in kernel data structures. The vulnerability specifically targets the interaction between l2tp sockets and inet sockets, creating a condition where malicious local users can manipulate kernel memory structures to achieve elevated privileges.
The technical root cause of this vulnerability stems from improper handling of socket data structures during the PPPoL2TP implementation. When an l2tp socket interacts with an inet socket, the kernel fails to properly validate or synchronize the differences between these two distinct socket types. This mismatch allows attackers to craft specific inputs that cause the kernel to dereference memory locations incorrectly, potentially leading to arbitrary code execution with kernel-level privileges. The vulnerability operates at the kernel level where memory management and socket operations intersect, making it particularly dangerous as it bypasses standard user-space protections.
From an operational perspective, this vulnerability presents a severe threat to systems running affected kernel versions, as local users can exploit it to gain root access without requiring external network connectivity or complex attack vectors. The attack requires only local system access, making it particularly concerning for multi-tenant environments, shared hosting platforms, or any system where local users might exist. The privilege escalation occurs through kernel memory corruption that can be leveraged to execute malicious code with the highest system privileges, effectively compromising the entire system. This vulnerability aligns with CWE-119 which addresses improper access to memory locations and represents a classic case of kernel memory corruption leading to privilege escalation.
The attack surface for this vulnerability includes any system utilizing PPPoL2TP functionality, particularly those with L2TP tunneling enabled or configured. Systems that have not applied the relevant kernel patches are at risk, and the impact extends beyond simple privilege escalation to potentially full system compromise. Organizations running kernel versions 3.15.6 or earlier should consider this vulnerability as a critical priority for remediation. The vulnerability demonstrates how seemingly isolated kernel subsystems can interact in unexpected ways to create security flaws that affect the entire system integrity.
Mitigation strategies for CVE-2014-4943 primarily focus on kernel version updates and system hardening measures. The most effective solution involves upgrading to kernel versions that contain the appropriate patches addressing the socket data structure mismatch. System administrators should also consider disabling PPPoL2TP functionality if it is not required for operations, as this eliminates the attack surface entirely. Additionally, implementing proper access controls and monitoring for unauthorized local access attempts can help detect potential exploitation attempts. The vulnerability highlights the importance of thorough testing of kernel subsystem interactions and proper validation of data structure handling in kernel space operations. Organizations should also consider implementing runtime protections and kernel module hardening to reduce the impact of such vulnerabilities. This case exemplifies why kernel security requires continuous attention and why proper code review processes are essential for preventing memory corruption vulnerabilities that can lead to privilege escalation.