CVE-2007-3104 in Linux
Summary
by MITRE
The sysfs_readdir function in the Linux kernel 2.6, as used in Red Hat Enterprise Linux (RHEL) 4.5 and other distributions, allows users to cause a denial of service (kernel OOPS) by dereferencing a null pointer to an inode in a dentry.
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Analysis
by VulDB Data Team • 07/21/2019
The vulnerability described in CVE-2007-3104 represents a critical kernel-level flaw in the Linux 2.6 operating system family that specifically affects the sysfs filesystem implementation. This issue manifests within the sysfs_readdir function which handles directory listing operations for the sysfs virtual filesystem. The vulnerability is particularly concerning because it allows unprivileged users to trigger a kernel panic or kernel oops condition that results in system instability and potential denial of service. The flaw occurs when the kernel attempts to dereference a null pointer to an inode structure within a dentry object, which is a fundamental data structure used by the kernel to represent filesystem entries. This type of null pointer dereference represents a classic kernel memory management error that can lead to system crashes and requires careful handling within kernel space operations.
The technical implementation of this vulnerability stems from improper validation of filesystem entry pointers within the sysfs subsystem. When a user performs directory listing operations on sysfs entries, the sysfs_readdir function processes dentry objects without adequate null pointer checks before accessing inode metadata. This particular flaw falls under the CWE-476 category of NULL Pointer Dereference, which is a well-documented weakness in software development that occurs when a program attempts to access memory through a null reference. The vulnerability is particularly dangerous because it operates at the kernel level where such faults can cause complete system failure rather than just application-level crashes. The impact is amplified by the fact that sysfs is a core filesystem used for exposing kernel objects to user space, making it accessible to all users on the system.
From an operational perspective, this vulnerability creates significant risks for enterprise environments where multiple users may have access to systems running affected kernel versions. The denial of service condition can be triggered through simple directory listing commands, making it easily exploitable by malicious users or attackers seeking to disrupt system availability. The kernel oops condition that results from this vulnerability typically manifests as a system crash or reboot, which can be particularly problematic in mission-critical environments where uptime is essential. According to ATT&CK framework categorization, this vulnerability aligns with the T1499.004 technique for Network Denial of Service, as it can be leveraged to cause system-wide availability issues. The vulnerability also maps to the privilege escalation category since it allows unprivileged users to cause kernel-level instability, potentially creating opportunities for further exploitation or system compromise.
Mitigation strategies for CVE-2007-3104 primarily focus on patch management and kernel updates to address the underlying null pointer dereference issue. System administrators should prioritize applying security patches from Red Hat and other vendors that contain fixes for this specific vulnerability. The recommended solution involves updating to kernel versions that properly validate dentry pointers before attempting to access associated inode structures. Additionally, implementing proper access controls and monitoring for unusual sysfs directory operations can help detect potential exploitation attempts. Organizations should also consider implementing kernel hardening techniques such as stack canaries, address space layout randomization, and kernel module signing to reduce the overall attack surface. The vulnerability highlights the importance of thorough code review and testing for kernel-level functions, particularly those handling filesystem operations where null pointer validation is critical for system stability and security.