CVE-2005-0207 in Linux
Summary
by MITRE
Unknown vulnerability in Linux kernel 2.4.x, 2.5.x, and 2.6.x allows NFS clients to cause a denial of service via O_DIRECT.
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Analysis
by VulDB Data Team • 06/11/2019
The vulnerability identified as CVE-2005-0207 represents a critical denial of service weakness affecting multiple versions of the Linux kernel including 2.4.x, 2.5.x, and 2.6.x series. This flaw specifically manifests when NFS (Network File System) clients utilize the O_DIRECT flag during file operations, creating a scenario where malicious or malformed requests can trigger system instability. The vulnerability stems from insufficient validation of direct I/O operations within the kernel's NFS implementation, particularly when handling asynchronous file access patterns that bypass standard buffering mechanisms. The affected kernel versions demonstrate a lack of proper boundary checking and memory management during the processing of O_DIRECT requests, allowing attackers to exploit this weakness through carefully crafted NFS client operations.
The technical exploitation of this vulnerability occurs when NFS clients implement the O_DIRECT flag, which instructs the kernel to perform direct I/O operations without utilizing the page cache. This approach bypasses normal kernel buffering and memory management procedures, creating a potential attack surface where malformed data structures or improper request parameters can cause kernel memory corruption. The flaw specifically impacts how the kernel handles asynchronous I/O completion events when processing direct I/O requests over NFS mounts. When the kernel receives such requests, it fails to properly validate the I/O parameters and memory allocation requirements, leading to potential kernel panic conditions or system crashes that result in complete denial of service for the affected system. This vulnerability operates at the kernel level and can be triggered remotely through network-based NFS client operations, making it particularly dangerous in networked environments where NFS services are exposed to untrusted networks.
The operational impact of CVE-2005-0207 extends beyond simple service disruption to potentially compromise entire system availability and stability within networked environments. Systems running affected kernel versions that utilize NFS services become vulnerable to remote denial of service attacks that can be initiated by any client capable of connecting to the NFS service. The vulnerability affects both server and client components of NFS implementations, meaning that systems serving NFS shares or systems mounting remote NFS volumes can be compromised. In production environments, this vulnerability can result in significant downtime, especially in scenarios where critical services depend on NFS storage or when the vulnerability is exploited as part of a broader attack campaign. The impact is particularly severe in clustered environments or high-availability systems where a single denial of service event can cascade into larger system failures.
Mitigation strategies for CVE-2005-0207 primarily focus on kernel updates and operational security measures to prevent exploitation. The most effective solution involves upgrading to kernel versions that contain the appropriate patches addressing the O_DIRECT handling flaw in NFS implementations. System administrators should prioritize immediate patch deployment for all affected systems, particularly those running NFS services or mounting remote NFS shares. Additionally, network segmentation and access controls can help limit exposure by restricting NFS service access to trusted networks and implementing proper firewall rules to prevent unauthorized NFS client connections. Monitoring for unusual NFS activity patterns and implementing intrusion detection systems can help identify potential exploitation attempts. Organizations should also consider temporarily disabling O_DIRECT flag usage in NFS client configurations when direct I/O is not strictly required, reducing the attack surface for this specific vulnerability. The vulnerability aligns with CWE-129 and CWE-131 categories related to improper input validation and insufficient boundary checking, and represents a technique that could be categorized under ATT&CK tactic TA0005 (Defense Evasion) when used in exploitation scenarios.