CVE-2008-0384 in OpenBSD
Summary
by MITRE
OpenBSD 4.2 allows local users to cause a denial of service (kernel panic) by calling the SIOCGIFRTLABEL IOCTL on an interface that does not have a route label, which triggers a NULL pointer dereference when the return value from the rtlabel_id2name function is not checked.
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Analysis
by VulDB Data Team • 10/14/2024
The vulnerability identified as CVE-2008-0384 represents a critical kernel-level flaw in OpenBSD 4.2 that demonstrates poor error handling practices in network interface management operations. This issue specifically affects the ioctl system call interface where the SIOCGIFRTLABEL command is used to retrieve route labels associated with network interfaces. The vulnerability arises from a fundamental failure in input validation and error checking within the kernel's network subsystem, creating a path where a local attacker can trigger a system-wide kernel panic through a seemingly benign operation.
The technical root cause of this vulnerability stems from a NULL pointer dereference condition that occurs when the rtlabel_id2name function returns a NULL value for interfaces without route labels. This function is responsible for mapping route label identifiers to their corresponding names, but fails to properly validate the return value before attempting to dereference it. The flaw exists in the kernel's network interface handling code where the SIOCGIFRTLABEL ioctl command does not adequately check whether the route label lookup operation succeeded before proceeding with subsequent operations. This type of vulnerability falls under CWE-476 which specifically addresses NULL pointer dereference conditions in software implementations.
The operational impact of this vulnerability extends beyond simple denial of service as it can completely compromise system stability and availability. When exploited, the kernel panic caused by this vulnerability results in an immediate system crash requiring manual reboot to restore normal operation. Local users with minimal privileges can leverage this flaw to disrupt network services, potentially affecting critical infrastructure components that depend on stable network connectivity. The vulnerability is particularly concerning because it can be triggered without requiring elevated privileges, making it accessible to any user account on the system. From an attack perspective, this vulnerability aligns with ATT&CK technique T1499.004 which involves network denial of service attacks, though in this case the attack vector is through legitimate system interfaces rather than external network traffic.
The exploitation of this vulnerability demonstrates a classic security flaw in kernel development practices where proper error handling and input validation were not implemented for all code paths. The lack of proper bounds checking and return value validation in the kernel's network subsystem creates a dangerous condition where user-controlled inputs can directly influence kernel memory operations. This type of vulnerability is particularly problematic in operating systems where kernel stability directly impacts overall system security posture and availability. The vulnerability also highlights the importance of thorough testing of edge cases in kernel code, particularly when dealing with network interface management operations that may encounter inconsistent or uninitialized data states.
Mitigation strategies for this vulnerability should focus on immediate patch application as provided by OpenBSD security advisories, along with implementing proper kernel memory protection mechanisms. System administrators should ensure that all kernel updates are applied promptly to address known vulnerabilities, particularly those that can be exploited by local users. Additional defensive measures include implementing network monitoring to detect unusual ioctl usage patterns and configuring system logging to capture kernel panic events for forensic analysis. The vulnerability underscores the necessity of comprehensive security testing for kernel-level code, including thorough validation of all return values from system calls and proper handling of error conditions in network interface operations. Organizations should also consider implementing privilege separation mechanisms to limit the potential impact of local privilege escalation attacks, even when kernel-level vulnerabilities exist.