CVE-2012-6638 in Linux
Summary
by MITRE • 01/25/2023
The tcp_rcv_state_process function in net/ipv4/tcp_input.c in the Linux kernel before 3.2.24 allows remote attackers to cause a denial of service (kernel resource consumption) via a flood of SYN+FIN TCP packets, a different vulnerability than CVE-2012-2663.
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Analysis
by VulDB Data Team • 01/25/2023
The vulnerability described in CVE-2012-6638 represents a critical denial of service flaw within the Linux kernel's TCP implementation that affects versions prior to 3.2.24. This weakness resides in the tcp_rcv_state_process function located in the net/ipv4/tcp_input.c source file, which handles incoming TCP packet processing in the kernel's network stack. The vulnerability specifically targets the handling of TCP packets in the connection establishment and termination phases, creating a scenario where remote attackers can exploit the kernel's resource management mechanisms to consume excessive system resources without proper validation of packet sequences.
The technical exploitation of this vulnerability occurs through the deliberate flooding of SYN+FIN TCP packets to target systems. When the kernel's tcp_rcv_state_process function receives these malformed packet combinations, it fails to properly validate the state transitions and packet ordering that should occur during TCP connection handling. This processing flaw causes the kernel to allocate resources for connection tracking and packet handling without proper bounds checking, leading to resource exhaustion that can ultimately result in system instability or complete denial of service conditions. The vulnerability operates independently from CVE-2012-2663, which affects different aspects of TCP state handling, making this a distinct yet equally serious threat to kernel stability.
From an operational perspective, this vulnerability presents significant risk to network infrastructure and server availability since attackers can consume kernel memory and processing resources through relatively simple network traffic patterns. The impact extends beyond individual system compromise to potentially affect entire network services, particularly affecting servers that handle high volumes of TCP connections or those with limited system resources. The resource consumption occurs at the kernel level where connection tracking structures and socket buffers are repeatedly allocated and processed without proper cleanup or rate limiting, creating a sustained consumption pattern that can exhaust system capabilities.
The vulnerability aligns with CWE-400, which addresses "Uncontrolled Resource Consumption" in software systems, specifically targeting kernel-level resource management failures. From an ATT&CK framework perspective, this vulnerability maps to T1499.004, "Endpoint Denial of Service," and T1595.001, "Network Denial of Service," as it enables attackers to consume system resources through network-based attacks. The exploitation pattern also reflects techniques described in T1071.004, "Application Layer Protocol: DNS," where network protocols are manipulated to cause system instability, though in this case the attack vector targets TCP protocol handling specifically. Organizations should implement immediate kernel updates to version 3.2.24 or later, while also considering network-level mitigations such as rate limiting and connection tracking restrictions to prevent exploitation of this vulnerability.
This flaw demonstrates the critical importance of proper state machine validation in kernel network stacks, where improper handling of protocol state transitions can create exploitable conditions. The vulnerability's persistence across multiple kernel versions indicates a fundamental design issue in TCP state processing that required significant kernel development attention to resolve properly. System administrators should prioritize patch management for this vulnerability, as the resource consumption pattern can be difficult to detect and may appear as legitimate traffic patterns until system performance degradation becomes apparent.