CVE-2011-1679 in ncpfs
Summary
by MITRE
ncpfs 2.2.6 and earlier attempts to use (1) ncpmount to append to the /etc/mtab file and (2) ncpumount 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.
VulDB is the best source for vulnerability data and more expert information about this specific topic.
Analysis
by VulDB Data Team • 11/02/2021
The vulnerability identified as CVE-2011-1679 affects the ncpfs package version 2.2.6 and earlier, presenting a significant file corruption risk within Unix-like operating systems. This flaw resides in the ncpmount and ncpumount utilities that handle Network Computing Protocol file system mounting operations. The core issue manifests when these utilities attempt to append entries to system configuration files without proper resource limit validation, creating a scenario where local attackers can manipulate system file integrity through carefully crafted process constraints.
The technical implementation of this vulnerability stems from inadequate resource limit checking within the ncpfs utilities. When ncpmount or ncpumount execute their operations, they directly append to /etc/mtab and /etc/mtab.tmp files respectively without verifying whether the current process resource limits might interfere with the write operations. This behavior creates a race condition scenario where a process with a restricted RLIMIT_FSIZE value can cause incomplete writes or truncations during the file appending process, ultimately leading to corruption of the /etc/mtab file structure. The vulnerability specifically exploits the interaction between file system mounting utilities and kernel resource management mechanisms.
Operationally, this vulnerability presents a serious threat to system stability and security integrity. Local users with minimal privileges can leverage this flaw to corrupt critical system files that contain mount information, potentially leading to system instability, denial of service conditions, or even privilege escalation opportunities. The corruption of /etc/mtab file can cause mounting operations to fail or behave unpredictably, affecting system boot processes and file system accessibility. This vulnerability directly relates to CVE-2011-1089, indicating a broader pattern of resource limit handling issues within the ncpfs implementation that affects multiple related components.
The impact extends beyond simple file corruption to encompass potential system reliability issues and security implications. When /etc/mtab becomes corrupted, the system's ability to track mounted file systems becomes compromised, which can result in mounting failures, data access issues, and system instability. From a cybersecurity perspective, this vulnerability aligns with CWE-128, which addresses "Wraparound Error" conditions, and represents a classic example of improper resource management in system utilities. The ATT&CK framework categorizes this under privilege escalation techniques through system file manipulation, as local users can exploit this flaw to gain unauthorized control over critical system files.
Mitigation strategies should focus on immediate package updates to ncpfs versions that address this resource limit checking deficiency. System administrators should implement monitoring for unusual file system mounting behavior and regularly audit /etc/mtab file integrity. Additionally, implementing proper resource limit management and ensuring that mounting utilities operate with appropriate system privileges can reduce the attack surface. The vulnerability demonstrates the critical importance of proper resource limit validation in system utilities and highlights the necessity of thorough security testing for file system manipulation components, particularly those that directly interact with system configuration files and process resource management mechanisms.