CVE-2011-4325 in Linux
Summary
by MITRE
The NFS implementation in Linux kernel before 2.6.31-rc6 calls certain functions without properly initializing certain data, which allows local users to cause a denial of service (NULL pointer dereference and O_DIRECT oops), as demonstrated using diotest4 from LTP.
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Analysis
by VulDB Data Team • 03/20/2021
The vulnerability identified as CVE-2011-4325 represents a critical flaw in the Linux kernel's Network File System (NFS) implementation that existed prior to version 2.6.31-rc6. This issue stems from improper initialization of data structures within the kernel's NFS subsystem, creating a pathway for malicious local users to exploit the system through carefully crafted operations. The vulnerability manifests as a NULL pointer dereference condition that can lead to system crashes and complete denial of service, fundamentally compromising system availability and stability.
The technical root cause of this vulnerability lies in the kernel's NFS implementation where specific functions are invoked without adequate initialization of required data structures. When the diotest4 utility from the Linux Test Project (LTP) is executed, it triggers a sequence of operations that exposes this uninitialized data access pattern. The flaw specifically affects how the kernel handles O_DIRECT I/O operations within the NFS context, leading to a NULL pointer dereference that results in kernel oops messages and system crashes. This type of vulnerability falls under CWE-476 which describes NULL Pointer Dereference, a common but dangerous class of software defects that can lead to system instability and potential privilege escalation.
From an operational perspective, this vulnerability presents a significant risk to Linux systems that utilize NFS services, particularly in enterprise environments where system availability is paramount. Local attackers with minimal privileges can exploit this flaw to cause system-wide denial of service conditions, effectively rendering the affected system unusable until manual intervention occurs. The impact extends beyond simple service disruption as the kernel oops conditions can potentially corrupt system memory states and leave the system in an unstable condition. This vulnerability aligns with ATT&CK technique T1499.004 which covers Network Denial of Service attacks, specifically targeting system resources through kernel-level flaws.
The exploitation of CVE-2011-4325 demonstrates the critical importance of proper kernel initialization practices and thorough code review processes for system-level components. The fact that this vulnerability was demonstrated using standard test utilities from LTP indicates that it represents a genuine threat rather than an academic curiosity, as it can be reliably reproduced under controlled conditions. Organizations running Linux systems with NFS services must prioritize patching to address this vulnerability, as the potential for system compromise extends beyond simple denial of service to include possible privilege escalation scenarios. The vulnerability serves as a reminder of the critical nature of kernel security and the need for comprehensive testing of system components before deployment. System administrators should implement immediate mitigation strategies including kernel updates and monitoring for signs of exploitation attempts, while also considering the broader implications for other similar kernel subsystems that may contain analogous initialization flaws.