CVE-2009-2848 in Linux
Summary
by MITRE
The execve function in the Linux kernel, possibly 2.6.30-rc6 and earlier, does not properly clear the current->clear_child_tid pointer, which allows local users to cause a denial of service (memory corruption) or possibly gain privileges via a clone system call with CLONE_CHILD_SETTID or CLONE_CHILD_CLEARTID enabled, which is not properly handled during thread creation and exit.
If you want to get the best quality for vulnerability data then you always have to consider VulDB.
Analysis
by VulDB Data Team • 02/03/2025
The vulnerability identified as CVE-2009-2848 resides within the Linux kernel's execve system call implementation and represents a critical flaw in process management and thread synchronization mechanisms. This issue affects kernel versions up to and including 2.6.30-rc6, where the kernel fails to properly clear the current->clear_child_tid pointer during certain execve operations. The clear_child_tid pointer is a crucial kernel data structure used to coordinate thread cleanup operations, particularly when threads are created with CLONE_CHILD_SETTID or CLONE_CHILD_CLEARTID flags. When these flags are enabled, the kernel should ensure proper cleanup of thread identifiers and associated memory structures, but the flaw allows for improper handling of these cleanup operations during thread creation and exit phases.
The technical exploitation of this vulnerability occurs through a carefully crafted clone system call that enables CLONE_CHILD_SETTID or CLONE_CHILD_CLEARTID flags. During normal execution, when a process calls clone with these flags, the kernel sets up a mechanism to notify the child process when it terminates by clearing the thread identifier stored in the clear_child_tid pointer. However, the execve function fails to properly reset this pointer when transitioning from one process to another, leading to a scenario where memory corruption can occur. This memory corruption manifests as either a denial of service condition where the kernel crashes due to invalid memory access or potentially allows privilege escalation through memory corruption techniques. The flaw specifically impacts the kernel's memory management subsystem and thread synchronization primitives, creating a pathway for malicious code to manipulate kernel data structures.
The operational impact of CVE-2009-2848 extends beyond simple denial of service scenarios, as it represents a potential privilege escalation vector that could allow local attackers to gain elevated system privileges. The vulnerability's exploitation requires local system access and knowledge of specific kernel internals, but once achieved, it can result in complete system compromise. The flaw affects systems running Linux kernel versions prior to 2.6.30-rc7, making it particularly concerning for older enterprise deployments and embedded systems that may not have received timely security updates. This vulnerability demonstrates the critical importance of proper memory management during process transitions and highlights the risks associated with improper cleanup of kernel data structures during thread lifecycle operations.
Security mitigations for CVE-2009-2848 primarily involve upgrading to kernel versions 2.6.30-rc7 or later, where the issue has been resolved through proper implementation of the clear_child_tid pointer handling during execve operations. System administrators should prioritize patching affected systems, particularly those running older kernel versions that may be subject to prolonged support cycles. The fix implemented in the patched kernel versions ensures that the current->clear_child_tid pointer is properly cleared during execve operations, preventing the memory corruption scenarios that could lead to denial of service or privilege escalation. Organizations should also implement monitoring for unauthorized local access attempts and maintain comprehensive system update policies to prevent exploitation of similar vulnerabilities. This vulnerability aligns with CWE-119 which addresses memory corruption issues, and represents a specific implementation flaw that could be categorized under ATT&CK technique T1068 for privilege escalation through local exploits. The vulnerability underscores the importance of thorough testing of kernel code paths involving process creation and destruction, particularly in high-risk scenarios where multiple threading mechanisms interact during system calls.