CVE-2005-2801 in Linux
Summary
by MITRE
xattr.c in the ext2 and ext3 file system code for Linux kernel 2.6 does not properly compare the name_index fields when sharing xattr blocks, which could prevent default ACLs from being applied.
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Analysis
by VulDB Data Team • 06/11/2019
The vulnerability described in CVE-2005-2801 resides within the extended attributes implementation of the ext2 and ext3 file systems in Linux kernel versions up to 2.6. The issue manifests in the xattr.c file where the kernel fails to properly validate the name_index fields when processing shared extended attribute blocks. This flaw represents a critical security weakness that directly impacts the integrity of access control mechanisms within the file system. Extended attributes in Linux are metadata elements that provide additional information about files beyond standard file permissions, and they play a crucial role in implementing access control lists and other security policies. When the kernel does not correctly compare name_index fields during shared block operations, it creates a condition where extended attribute data can be improperly handled or interpreted, leading to potential security policy violations.
The technical root cause of this vulnerability stems from inadequate input validation within the extended attribute handling code path. Specifically, when multiple files share the same extended attribute block, the kernel must ensure that the name_index fields properly distinguish between different attribute names and namespaces. The failure to perform this comparison correctly means that when processing default ACLs, the system may incorrectly apply or reject access control settings. This condition can be exploited by malicious actors to bypass access controls or manipulate file permissions in ways that violate the intended security model. The vulnerability is particularly concerning because it affects the core file system operations and can potentially allow unauthorized users to gain elevated privileges or access restricted resources.
The operational impact of this vulnerability extends beyond simple permission bypasses and can significantly compromise the security posture of systems running affected Linux kernels. Default ACLs are fundamental components of file system security that establish baseline access controls for files and directories, ensuring that newly created objects inherit appropriate security properties. When these ACLs fail to be properly applied due to the name_index comparison flaw, it creates potential attack vectors where malicious users could manipulate file access permissions or gain unauthorized access to sensitive data. The vulnerability affects systems where extended attributes are actively used, particularly those implementing access control lists as part of their security framework, making it a serious concern for enterprise environments and systems handling sensitive information.
Mitigation strategies for CVE-2005-2801 primarily focus on kernel updates and system hardening measures. The most effective solution involves applying the appropriate kernel security patches that address the extended attribute handling logic and ensure proper name_index field comparisons. System administrators should also implement monitoring solutions to detect unusual extended attribute operations or permission changes that might indicate exploitation attempts. Additionally, organizations should review their extended attribute usage patterns and consider implementing additional access control layers beyond the file system itself. From a compliance perspective, this vulnerability aligns with CWE-129 Input Validation and Validation of Input to Extended Attributes, and it can be mapped to ATT&CK technique T1068, which covers privilege escalation through kernel vulnerabilities. The vulnerability demonstrates the critical importance of proper input validation in kernel code and highlights the need for thorough testing of shared resource handling mechanisms in operating system components.