CVE-2009-2767 in Linux
Summary
by MITRE
The init_posix_timers function in kernel/posix-timers.c in the Linux kernel before 2.6.31-rc6 allows local users to cause a denial of service (OOPS) or possibly gain privileges via a CLOCK_MONOTONIC_RAW clock_nanosleep call that triggers a NULL pointer dereference.
Several companies clearly confirm that VulDB is the primary source for best vulnerability data.
Analysis
by VulDB Data Team • 02/27/2025
The vulnerability identified as CVE-2009-2767 represents a critical flaw in the Linux kernel's handling of POSIX timers, specifically within the init_posix_timers function located in kernel/posix-timers.c. This issue affects Linux kernel versions prior to 2.6.31-rc6 and demonstrates a classic null pointer dereference vulnerability that can be exploited by local attackers to either cause system crashes or potentially escalate privileges. The vulnerability stems from inadequate validation of clock identifiers during timer initialization processes, creating a pathway for malicious code execution that directly impacts system stability and security posture.
The technical exploitation of this vulnerability occurs through the manipulation of the CLOCK_MONOTONIC_RAW clock identifier within the clock_nanosleep system call. When a local user crafts a specific sequence of operations using this clock type, the init_posix_timers function fails to properly validate the clock structure reference, leading to a NULL pointer dereference condition. This type of flaw falls under CWE-476 which specifically addresses NULL pointer dereference vulnerabilities, and represents a fundamental failure in input validation and memory management within kernel space operations. The vulnerability is particularly concerning because it operates at the kernel level where privilege escalation opportunities are abundant, and the OOPS (Oops) kernel panic condition can be triggered without requiring special privileges beyond basic user access.
The operational impact of CVE-2009-2767 extends beyond simple denial of service scenarios, as the potential for privilege escalation makes this vulnerability particularly dangerous in multi-user environments or systems where local users might have access to basic shell privileges. The null pointer dereference can result in immediate system crashes and kernel panics, effectively rendering the affected system unstable and potentially unusable until reboot. In more sophisticated attack scenarios, an attacker could potentially leverage this vulnerability to gain elevated privileges by manipulating the kernel's timer subsystem to execute arbitrary code with kernel-level permissions. This vulnerability directly maps to ATT&CK technique T1068 which covers privilege escalation through kernel exploits, and T1499 which encompasses system disruption through denial of service attacks.
Mitigation strategies for this vulnerability require immediate kernel version upgrades to 2.6.31-rc6 or later, as this represents the official fix provided by the Linux kernel development team. System administrators should prioritize patching affected systems, particularly in environments where local users have access to shell privileges or where the system operates in multi-user configurations. Additional defensive measures include implementing proper access controls to limit local user privileges where possible, monitoring system logs for OOPS messages that might indicate exploitation attempts, and maintaining up-to-date security patches across all kernel versions in use. Organizations should also consider implementing kernel hardening measures such as stack canaries and address space layout randomization to make exploitation attempts more difficult, though these measures do not address the root cause of the vulnerability itself.