CVE-2007-2875 in Linux
Summary
by MITRE
Integer underflow in the cpuset_tasks_read function in the Linux kernel before 2.6.20.13, and 2.6.21.x before 2.6.21.4, when the cpuset filesystem is mounted, allows local users to obtain kernel memory contents by using a large offset when reading the /dev/cpuset/tasks file.
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Analysis
by VulDB Data Team • 07/20/2019
The vulnerability identified as CVE-2007-2875 represents a critical integer underflow flaw within the Linux kernel's cpuset subsystem that affects versions prior to 2.6.20.13 and 2.6.21.4. This vulnerability resides in the cpuset_tasks_read function which handles reading operations from the /dev/cpuset/tasks file when the cpuset filesystem is mounted. The cpuset filesystem is a virtual filesystem that allows processes to be organized into hierarchical groups and restricts their access to specific CPU cores and memory nodes. When a local user performs a read operation on the tasks file with a large offset value, the integer underflow condition occurs, leading to unpredictable behavior in memory access patterns.
The technical exploitation of this vulnerability stems from improper input validation within the kernel's cpuset implementation. Specifically, when processing read requests for the cpuset/tasks file, the kernel fails to properly validate the offset parameter, allowing an attacker to supply a value that, when processed, results in an integer underflow. This underflow condition causes the kernel to interpret memory addresses incorrectly, potentially leading to the exposure of kernel memory contents. The vulnerability is classified as a CWE-191 Integer Underflow (Wrap or Wraparound) which is a well-documented weakness in software systems where arithmetic operations produce results that fall below the minimum value representable by the data type. This particular implementation flaw allows for information disclosure that can reveal sensitive kernel memory structures, potentially including stack contents, kernel variables, or other confidential information.
The operational impact of this vulnerability extends beyond simple information disclosure, as it provides attackers with access to kernel memory that could be leveraged for further exploitation. Local users who can access the cpuset filesystem can exploit this condition to read kernel memory contents, which may contain sensitive information such as cryptographic keys, user credentials, or other confidential data stored in kernel memory. The vulnerability is particularly concerning because it operates at the kernel level where attackers can gain access to privileged information that would normally be protected from user-space access. This type of information disclosure vulnerability aligns with the ATT&CK technique T1005 - Data from Local System, where adversaries attempt to gather data from the local system, and T1059 - Command and Scripting Interpreter, as attackers may use the leaked information to craft more sophisticated attacks. The vulnerability also represents a path to privilege escalation since knowledge of kernel memory contents can be used to identify potential weaknesses in kernel structures or to develop more targeted exploits.
Mitigation strategies for CVE-2007-2875 focus primarily on patching the affected kernel versions to include proper input validation and integer overflow protection. System administrators should immediately update to kernel versions 2.6.20.13 or 2.6.21.4 and later, which contain the necessary fixes for this vulnerability. Additionally, organizations should consider implementing access controls to limit who can mount and interact with cpuset filesystems, particularly in environments where untrusted users may have access to the system. The patch addresses the root cause by ensuring proper validation of the offset parameter in the cpuset_tasks_read function, preventing the integer underflow condition that leads to memory exposure. Security monitoring should also be enhanced to detect unusual patterns of access to cpuset filesystems, as this vulnerability may be exploited as part of a broader attack campaign. Organizations should also review their kernel configuration to ensure that cpuset functionality is only enabled when absolutely necessary, reducing the attack surface for potential exploitation. The vulnerability demonstrates the importance of robust input validation in kernel space code and highlights the critical need for thorough security testing of kernel subsystems that handle user input, particularly those dealing with memory management and file system operations.