CVE-2007-5500 in Linux
Summary
by MITRE
The wait_task_stopped function in the Linux kernel before 2.6.23.8 checks a TASK_TRACED bit instead of an exit_state value, which allows local users to cause a denial of service (machine crash) via unspecified vectors. NOTE: some of these details are obtained from third party information.
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Analysis
by VulDB Data Team • 08/01/2019
The vulnerability identified as CVE-2007-5500 represents a critical flaw in the Linux kernel's process management subsystem that existed prior to version 2.6.23.8. This issue stems from an incorrect implementation within the wait_task_stopped function which is responsible for handling process state transitions and synchronization. The flaw manifests when the kernel attempts to determine whether a task has stopped execution, a fundamental operation required for proper process control and debugging functionality. The vulnerability specifically involves a logic error where the kernel incorrectly evaluates the TASK_TRACED bit rather than examining the proper exit_state value that indicates a process's actual termination state. This misinterpretation creates a scenario where the kernel's process management logic becomes confused about the true state of terminated processes, leading to unpredictable behavior in the kernel's task handling mechanisms.
The technical nature of this vulnerability places it firmly within the domain of kernel-level logic errors that can be exploited to cause system instability. According to CWE classification, this represents a weakness in the kernel's state management logic, specifically categorized as CWE-691 where insufficient control flow management leads to potential system crashes. The flaw operates at a low level within the kernel's process control block handling, where the TASK_TRACED bit is a flag used to indicate when a process is being traced by a debugger or monitoring tool, while exit_state represents the actual termination state of a process. The improper checking of these values creates a condition where a local attacker can manipulate process states in such a way that the kernel's internal consistency checks fail, ultimately resulting in a system crash. This type of vulnerability is particularly dangerous because it operates within kernel space where privilege escalation is not required for exploitation, and the impact is immediate and severe.
From an operational perspective, this vulnerability presents a significant risk to Linux systems as it allows local users to trigger a denial of service condition that can bring down entire machines. The attack vector is particularly concerning because it requires only local access to the system, making it accessible to any user with shell access or basic system privileges. The exploitability of this vulnerability means that an attacker could potentially cause repeated system crashes, leading to persistent availability issues that could be used for both disruptive attacks and system compromise. The fact that this vulnerability affects the core kernel functionality means that any service or application relying on proper process management could be impacted, potentially affecting system stability and reliability. The issue demonstrates how subtle logic errors in kernel code can have catastrophic effects on system integrity, as the kernel's process management is fundamental to all system operations.
The mitigation strategies for CVE-2007-5500 center around applying the appropriate kernel security patches that address the specific logic error in the wait_task_stopped function. System administrators should immediately upgrade to Linux kernel versions 2.6.23.8 or later where this vulnerability has been corrected through proper implementation of state checking logic. The fix ensures that the kernel correctly evaluates the exit_state value rather than relying on the potentially misleading TASK_TRACED bit for process state determination. Additionally, organizations should implement proper access controls and privilege management to limit local user access where possible, though this does not address the vulnerability itself. From an ATT&CK framework perspective, this vulnerability aligns with techniques involving privilege escalation and denial of service, as it allows local users to cause system instability without requiring elevated privileges. The vulnerability also relates to defense evasion techniques since it operates at the kernel level where detection is difficult and the impact is immediate, making it a preferred vector for attackers seeking to disrupt system availability. Organizations should also consider implementing monitoring solutions that can detect anomalous process behavior patterns that might indicate exploitation attempts.