CVE-2011-1749 in nfs-utils
Summary
by MITRE
The nfs_addmntent function in support/nfs/nfs_mntent.c in the mount.nsf tool in nfs-utils before 1.2.4 attempts to append to the /etc/mtab file without first checking whether resource limits would interfere, which allows local users to corrupt this 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 • 04/12/2025
The vulnerability identified as CVE-2011-1749 resides within the nfs-utils package, specifically in the mount.nfs tool's handling of the /etc/mtab file. This flaw represents a classic example of improper resource management and file system manipulation that can lead to system instability and potential security compromise. The issue affects versions of nfs-utils prior to 1.2.4, making it a significant concern for systems that rely on Network File System mounting operations. The vulnerability manifests when the nfs_addmntent function attempts to append entries to the /etc/mtab file without proper validation of system resource constraints, creating an exploitable condition that can be leveraged by local attackers.
The technical flaw in CVE-2011-1749 stems from the absence of resource limit checking before file operations. When a process attempts to write to /etc/mtab, it must comply with the system's RLIMIT_FSIZE setting which controls the maximum size of files that can be created. The function fails to verify whether the current process resource limits would prevent successful file appending, particularly when RLIMIT_FSIZE is set to a small value. This oversight allows malicious users to craft processes with constrained file size limits that would normally prevent file corruption, yet the nfs_addmntent function does not account for this constraint during its file manipulation operations. The vulnerability operates under the broader context of improper handling of file system resources and lacks proper error checking mechanisms that should validate system constraints before attempting file modifications.
The operational impact of this vulnerability extends beyond simple file corruption, as the /etc/mtab file serves as a critical system component that tracks mounted file systems. When this file becomes corrupted, it can lead to system instability, incorrect mount point reporting, and potentially prevent proper system operation. The corruption can manifest in various ways including truncated entries, malformed data, or complete file overwrite scenarios that can disrupt the normal functioning of the mount system. This vulnerability particularly affects systems where local users might have limited privileges but can manipulate process resource limits, making it a concern for multi-user environments where privilege separation is not properly enforced. The issue is closely related to CVE-2011-1089, indicating a pattern of resource management flaws within the nfs-utils package that require comprehensive security auditing.
Security mitigations for CVE-2011-1749 involve upgrading to nfs-utils version 1.2.4 or later, which contains the necessary patches to properly check resource limits before file operations. System administrators should also implement proper monitoring of /etc/mtab file integrity and establish regular backup procedures to ensure recovery capabilities in case of corruption. The vulnerability aligns with CWE-772, which addresses missing resource cleanup, and can be mapped to ATT&CK technique T1059.007 for privilege escalation through local exploitation. Organizations should conduct thorough vulnerability assessments to identify systems running vulnerable versions of nfs-utils and ensure proper patch management protocols are in place to prevent exploitation. Additionally, implementing proper access controls and monitoring of system resource limits can provide additional defense-in-depth measures against similar vulnerabilities.