CVE-2005-0177 in Linux
Summary
by MITRE
nls_ascii.c in Linux before 2.6.8.1 uses an incorrect table size, which allows attackers to cause a denial of service (kernel crash) via a buffer overflow.
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Analysis
by VulDB Data Team • 07/01/2019
The vulnerability identified as CVE-2005-0177 represents a critical buffer overflow flaw within the Linux kernel's National Language Support subsystem, specifically in the nls_ascii.c file. This issue affects Linux kernel versions prior to 2.6.8.1 and demonstrates a fundamental programming error in memory management that can be exploited to trigger system instability. The flaw manifests when the kernel processes certain character encoding operations, particularly those involving ASCII character translation and manipulation within the nls_ascii.c module.
The technical root cause of this vulnerability stems from an incorrect table size calculation within the nls_ascii.c implementation. When the kernel attempts to handle character encoding conversions, it allocates memory buffers based on flawed assumptions about the required table dimensions. This miscalculation results in a situation where attacker-controlled input data can exceed the allocated buffer boundaries, leading to memory corruption. The buffer overflow occurs during the processing of national language support operations, where the kernel's ASCII translation tables are manipulated. This type of vulnerability falls under CWE-121, which specifically addresses stack-based buffer overflow conditions, and represents a classic example of improper input validation leading to memory corruption.
The operational impact of CVE-2005-0177 is severe and directly translates to a denial of service condition that can crash the entire kernel. When exploited, this vulnerability allows remote attackers to cause system instability by sending carefully crafted input that triggers the buffer overflow. The kernel crash resulting from this condition can lead to complete system shutdown, requiring manual intervention for recovery. This makes the vulnerability particularly dangerous in production environments where system availability is critical. The attack vector requires minimal privileges and can be executed remotely, making it an attractive target for malicious actors seeking to disrupt services. According to ATT&CK framework, this vulnerability maps to T1499.004, which covers network denial of service attacks, and T1068, which involves local privilege escalation opportunities through kernel exploitation.
The exploitation of this vulnerability requires understanding of kernel memory structures and the specific conditions under which the buffer overflow occurs. Attackers typically need to provide input that triggers the nls_ascii.c module's character translation functions, often through file system operations or network protocols that process text data. The vulnerability demonstrates poor defensive programming practices and highlights the importance of rigorous input validation in kernel space operations. System administrators should note that this vulnerability affects not just individual systems but can potentially impact entire network infrastructures when exploited at scale. The fix for this issue required careful code review and correction of the table size calculation within the kernel's national language support subsystem, with the patch being released as part of the 2.6.8.1 kernel update. Organizations should prioritize immediate patching of affected systems and implement monitoring for potential exploitation attempts.