CVE-2011-1675 in Linux
Summary
by MITRE
mount in util-linux 2.19 and earlier attempts to append to the /etc/mtab.tmp file without first checking whether resource limits would interfere, which allows local users to trigger corruption of the /etc/mtab file via a process with a small RLIMIT_FSIZE value, a related issue to CVE-2011-1089.
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Analysis
by VulDB Data Team • 11/02/2021
The vulnerability identified as CVE-2011-1675 affects the mount utility in util-linux versions 2.19 and earlier, presenting a significant security risk through improper handling of file system resource limits. This flaw specifically targets the /etc/mtab.tmp file manipulation process during mount operations, where the system fails to validate whether current resource limitations might interfere with the append operation. The issue stems from a lack of proper resource limit checking before file system modifications occur, creating an avenue for privilege escalation and system integrity compromise. The vulnerability is particularly concerning because it leverages existing system resource constraints to cause unintended file corruption, making it difficult to detect and prevent through standard security measures.
The technical exploitation of this vulnerability occurs when a local user with a process running under a restricted RLIMIT_FSIZE value attempts to perform mount operations that would write to /etc/mtab.tmp. This specific resource limit prevents the process from writing beyond a certain file size threshold, but the mount utility does not account for this constraint during its file append operations. When the system attempts to append to the temporary file, the write operation fails due to the resource limit restriction, yet the mount utility continues processing without proper error handling. This results in partial writes or incomplete file operations that ultimately corrupt the /etc/mtab file structure. The flaw aligns with CWE-128, which addresses the improper handling of resource limits during file system operations, and demonstrates how seemingly benign system constraints can be exploited to create persistent security issues.
The operational impact of CVE-2011-1675 extends beyond simple file corruption, potentially affecting system stability and integrity across multiple operational domains. When the /etc/mtab file becomes corrupted, it can cause mount and unmount operations to fail, leading to system instability and potential denial of service conditions. The corruption may also affect other system utilities that depend on accurate mount table information, creating cascading failures throughout the system's file system management capabilities. This vulnerability particularly affects systems where users might have the ability to modify their own process resource limits, which is common in multi-user environments or shared hosting scenarios. The related issue to CVE-2011-1089 further emphasizes the pattern of improper resource limit handling in system utilities, indicating a broader class of vulnerabilities within the util-linux package that require comprehensive patching and system hardening.
Mitigation strategies for CVE-2011-1675 must address both immediate patching requirements and long-term system hardening approaches to prevent exploitation. The primary solution involves upgrading to util-linux version 2.20 or later, where the mount utility properly checks resource limits before attempting file operations. System administrators should also implement monitoring for processes that attempt to modify resource limits in ways that could trigger this vulnerability, particularly focusing on RLIMIT_FSIZE changes that might be used maliciously. The ATT&CK framework categorizes this vulnerability under privilege escalation techniques, specifically targeting the 'File System Permissions Modification' and 'Resource Hijacking' tactics, making it important for security teams to monitor for related behavioral patterns. Additionally, implementing proper access controls to limit who can modify resource limits and ensuring that system utilities are run with appropriate privileges can help prevent exploitation of this class of vulnerabilities. Organizations should also consider implementing regular file integrity monitoring for critical system files like /etc/mtab to detect corruption early and maintain system stability.