CVE-2007-5908 in Linux
Summary
by MITRE
** REJECT ** Buffer overflow in the (1) sysfs_show_available_clocksources and (2) sysfs_show_current_clocksources functions in Linux kernel 2.6.23 and earlier might allow local users to cause a denial of service or execute arbitrary code via crafted clock source names. NOTE: follow-on analysis by Linux developers states that "There is no way for unprivileged users (or really even the root user) to add new clocksources."
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Analysis
by VulDB Data Team • 04/13/2019
The vulnerability identified as CVE-2007-5908 represents a buffer overflow condition within the Linux kernel's sysfs interface, specifically affecting kernel versions 2.6.23 and earlier. This flaw manifests in two distinct functions: sysfs_show_available_clocksources and sysfs_show_current_clocksources, which handle the display of clock source information through the sysfs filesystem interface. The vulnerability arises from inadequate input validation when processing clock source names, creating a scenario where malicious input can exceed the bounds of allocated memory buffers.
The technical implementation of this vulnerability stems from improper bounds checking in kernel space code that manages clock source enumeration. When the kernel processes clock source names through these functions, it fails to properly validate the length of input strings before copying them into fixed-size buffers. This classic buffer overflow condition can be exploited by local users who craft malicious clock source names that exceed the allocated buffer space, potentially leading to memory corruption. The vulnerability operates at the kernel level, meaning that successful exploitation could result in either a system crash through denial of service or more critically, arbitrary code execution within kernel context.
From an operational perspective, this vulnerability presents a significant risk to system integrity and availability. The potential for local privilege escalation exists because kernel memory corruption can be leveraged to execute arbitrary code with the highest system privileges. The impact extends beyond simple denial of service to encompass full system compromise, as attackers could potentially gain root access or manipulate critical kernel data structures. The vulnerability's local nature means that any user with access to the system could potentially exploit it, though the follow-on analysis indicates that the attack surface is limited by the inability of unprivileged users to add new clock sources, which reduces the practical exploitation vectors.
The mitigation strategies for this vulnerability primarily involve applying kernel updates to versions 2.6.24 and later, where the buffer overflow conditions have been addressed through proper input validation and bounds checking. System administrators should prioritize patching affected systems, particularly those running kernel versions 2.6.23 or earlier. Additionally, implementing proper access controls and monitoring for unusual sysfs activity can help detect potential exploitation attempts. Security frameworks such as the Common Weakness Enumeration categorize this issue as a buffer overflow vulnerability, while the MITRE ATT&CK framework would classify this under privilege escalation and execution techniques. Organizations should also consider implementing kernel hardening measures including stack canaries, address space layout randomization, and kernel module signing to further reduce the exploitation risk. The vulnerability highlights the critical importance of thorough input validation in kernel space code and demonstrates how seemingly minor flaws in system interfaces can lead to severe security implications.