CVE-2005-3275 in Linux
Summary
by MITRE
The NAT code (1) ip_nat_proto_tcp.c and (2) ip_nat_proto_udp.c in Linux kernel 2.6 before 2.6.13 and 2.4 before 2.4.32-rc1 incorrectly declares a variable to be static, which allows remote attackers to cause a denial of service (memory corruption) by causing two packets for the same protocol to be NATed at the same time, which leads to memory corruption.
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Analysis
by VulDB Data Team • 06/14/2019
The vulnerability described in CVE-2005-3275 represents a critical memory corruption issue within the Linux kernel's Network Address Translation implementation, specifically affecting versions prior to 2.6.13 and 2.4.32-rc1. This flaw exists in the NAT code modules ip_nat_proto_tcp.c and ip_nat_proto_udp.c which handle protocol-specific NAT operations for tcp and udp traffic respectively. The issue stems from an improper variable declaration that creates a race condition when processing packets for the same protocol simultaneously, potentially leading to system instability and denial of service conditions.
The technical root cause of this vulnerability lies in the incorrect static variable declaration within the NAT processing functions. When multiple packets belonging to the same protocol are processed concurrently through the NAT mechanism, the static variable's improper scope and lifetime management causes memory corruption. This memory corruption occurs because the static variable, which should have local scope within the function context, retains its value across multiple function calls, leading to unpredictable behavior when packet processing overlaps. The flaw is classified under CWE-665 as improper initialization of a variable, specifically manifesting as incorrect static variable usage in a multi-threaded or concurrent processing environment.
The operational impact of this vulnerability is severe, as it allows remote attackers to trigger a denial of service condition through carefully crafted packet sequences. An attacker can exploit this by sending two packets for the same protocol that will be processed through NAT simultaneously, causing the memory corruption that leads to system instability. This vulnerability essentially creates a path for remote attackers to compromise system availability by forcing the kernel into an inconsistent state through memory corruption. The attack vector requires minimal privileges and can be executed from remote locations, making it particularly dangerous in networked environments.
This vulnerability aligns with ATT&CK technique T1499.004 which covers "Endpoint Denial of Service" and specifically targets the kernel's network processing capabilities. The flaw demonstrates the importance of proper variable scoping in kernel code, where improper static variable usage in concurrent environments can lead to memory corruption. The vulnerability also relates to the broader category of kernel memory management issues that can be exploited to cause system crashes or require system rebooting. Organizations should implement immediate mitigation strategies including kernel updates to versions 2.6.13 or 2.4.32-rc1 and higher, along with network monitoring to detect potential exploitation attempts.
The fix for this vulnerability involved correcting the variable declarations in the NAT code modules to ensure proper scope and lifetime management of variables within the packet processing functions. This correction prevents the race condition that previously led to memory corruption when handling concurrent packet processing. System administrators should prioritize patching affected systems and monitoring for exploitation attempts, as the vulnerability can be leveraged to cause significant disruption to network services. The issue highlights the critical need for thorough code review processes in kernel development, particularly for concurrent processing scenarios where variable lifetime management becomes crucial for system stability and security.