CVE-2013-4163 in Linux
Summary
by MITRE
The ip6_append_data_mtu function in net/ipv6/ip6_output.c in the IPv6 implementation in the Linux kernel through 3.10.3 does not properly maintain information about whether the IPV6_MTU setsockopt option had been specified, which allows local users to cause a denial of service (BUG and system crash) via a crafted application that uses the UDP_CORK option in a setsockopt system call.
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Analysis
by VulDB Data Team • 05/20/2021
The vulnerability identified as CVE-2013-4163 resides within the Linux kernel's IPv6 implementation, specifically in the ip6_append_data_mtu function located in net/ipv6/ip6_output.c. This flaw affects Linux kernel versions through 3.10.3 and represents a critical security issue that can be exploited by local attackers to trigger system crashes and denial of service conditions. The vulnerability stems from improper handling of the IPV6_MTU setsockopt option within the IPv6 output path, creating a condition where the kernel fails to accurately track whether this specific socket option has been explicitly configured by an application.
The technical root cause of this vulnerability lies in the function's failure to properly maintain state information regarding the IPV6_MTU setsockopt option. When applications use the UDP_CORK option in conjunction with setsockopt system calls, the kernel's IPv6 implementation does not correctly preserve the knowledge of whether the IPV6_MTU option was previously specified. This state management error creates a scenario where the kernel's internal data structures become inconsistent, leading to a BUG condition that ultimately results in system crashes. The flaw manifests during the processing of IPv6 packets when the kernel attempts to handle the MTU information inappropriately, causing the kernel to execute code paths that lead to system instability.
The operational impact of this vulnerability is significant as it allows local users to perform a denial of service attack against the target system. An attacker can craft a malicious application that leverages both the UDP_CORK option and the setsockopt system call to exploit this flaw. The consequence is a system crash that can be repeated multiple times, effectively rendering the system unavailable to legitimate users. This vulnerability particularly affects systems running Linux kernel versions up to 3.10.3 where the flawed code path remains unpatched. The attack vector requires local access to the system, making it a local privilege escalation or lateral movement concern rather than a remote exploit, though it can still severely impact system availability and stability.
From a cybersecurity perspective, this vulnerability aligns with CWE-119 which addresses improper restriction of operations within a recognized security boundary, and represents a classic case of memory corruption that leads to system instability. The ATT&CK framework would categorize this under privilege escalation and denial of service tactics, as local users can leverage this flaw to compromise system availability. The vulnerability demonstrates poor input validation and state management within kernel space code, highlighting the critical importance of maintaining proper state tracking in security-sensitive components. Organizations should immediately apply kernel updates to address this vulnerability and ensure that systems running affected kernel versions are patched to prevent exploitation. The flaw underscores the necessity of thorough code review and testing of kernel-level functions that handle network protocol operations, particularly those involving socket options and packet processing.
The remediation approach involves updating to Linux kernel versions that contain the appropriate patches addressing this specific state management issue in the ip6_append_data_mtu function. System administrators should prioritize patching affected systems and monitor for any signs of exploitation attempts. Additionally, implementing proper access controls and monitoring for unusual socket option usage patterns can help detect potential exploitation attempts. The vulnerability serves as a reminder of the critical nature of kernel security and the need for continuous security assessment of core system components that handle network communications.