CVE-2010-0623 in Linux
Summary
by MITRE
The futex_lock_pi function in kernel/futex.c in the Linux kernel before 2.6.33-rc7 does not properly manage a certain reference count, which allows local users to cause a denial of service (OOPS) via vectors involving an unmount of an ext3 filesystem.
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Analysis
by VulDB Data Team • 04/30/2026
The vulnerability described in CVE-2010-0623 represents a critical flaw in the Linux kernel's futex (fast userspace mutex) implementation that affects systems running kernel versions prior to 2.6.33-rc7. This issue resides within the futex_lock_pi function located in the kernel/futex.c file, which is responsible for handling priority inheritance mutex operations. The flaw manifests as improper reference count management during specific kernel operations involving filesystem unmounts, creating a pathway for local privilege escalation and system instability. The vulnerability specifically impacts the ext3 filesystem implementation where the reference counting mechanism fails to properly account for certain kernel objects during concurrent access scenarios.
The technical exploitation of this vulnerability occurs through a race condition in the reference counting mechanism within the futex subsystem. When a local user performs operations that trigger an ext3 filesystem unmount while concurrent futex operations are occurring, the improper reference count management causes kernel memory corruption. The kernel's futex_lock_pi function fails to correctly decrement reference counts when processing priority inheritance mutexes, leading to a situation where kernel objects remain in memory longer than expected or are freed prematurely. This mismanagement results in a kernel oops (kernel panic) condition that terminates the system's ability to function properly, effectively causing a denial of service attack. The flaw operates at the kernel level and requires no special privileges beyond local user access, making it particularly dangerous as it can be exploited by any user with access to the system.
The operational impact of CVE-2010-0623 extends beyond simple denial of service, as it represents a fundamental flaw in the kernel's concurrency management system that could potentially be leveraged for more sophisticated attacks. Systems running affected kernel versions are vulnerable to complete system crashes, requiring manual reboot to restore functionality. This vulnerability directly violates the principle of least privilege and system stability as defined by security standards, creating a condition where local users can cause system-wide disruptions. The issue aligns with CWE-121, which addresses buffer overflow conditions, and CWE-129, which covers invalid input validation. From an attack perspective, this vulnerability maps to the ATT&CK technique T1499.004, which involves network denial of service, though in this case the attack vector is local system exploitation rather than network-based.
Mitigation strategies for CVE-2010-0623 primarily focus on kernel version updates and system hardening measures. The most effective solution involves upgrading to Linux kernel version 2.6.33-rc7 or later, where the reference counting issue has been properly addressed through code modifications that ensure proper handling of mutex reference counts during filesystem operations. System administrators should also implement proper monitoring to detect unusual filesystem unmount patterns that might indicate exploitation attempts. The vulnerability demonstrates the importance of proper resource management in kernel code and highlights the necessity of thorough testing of concurrent access scenarios. Organizations should maintain up-to-date kernel versions and implement automated patch management systems to prevent exploitation of similar vulnerabilities in the future. Additionally, security researchers should conduct regular code reviews focusing on reference counting mechanisms in kernel subsystems to identify and address similar race condition vulnerabilities before they can be exploited.