CVE-2009-3288 in Linux
Summary
by MITRE
The sg_build_indirect function in drivers/scsi/sg.c in Linux kernel 2.6.28-rc1 through 2.6.31-rc8 uses an incorrect variable when accessing an array, which allows local users to cause a denial of service (kernel OOPS and NULL pointer dereference), as demonstrated by using xcdroast to duplicate a CD. NOTE: this is only exploitable by users who can open the cdrom device.
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Analysis
by VulDB Data Team • 08/23/2021
The vulnerability identified as CVE-2009-3288 represents a critical flaw in the Linux kernel's SCSI generic (sg) subsystem that affects versions 2.6.28-rc1 through 2.6.31-rc8. This issue resides within the sg_build_indirect function located in drivers/scsi/sg.c, where a programming error manifests as an incorrect variable usage during array access operations. The flaw specifically involves a null pointer dereference condition that can be triggered by local users with access to cdrom devices, making it particularly concerning for systems where user privileges are not strictly controlled.
The technical implementation of this vulnerability stems from a coding error where the kernel function incorrectly references a variable when performing array operations, leading to improper memory access patterns. When the sg_build_indirect function processes SCSI commands through the generic SCSI interface, it encounters a scenario where a NULL pointer is dereferenced due to the incorrect variable substitution. This memory access violation results in a kernel oops condition and subsequent system crash, effectively causing a denial of service that renders the affected system unstable and unresponsive. The exploitation vector is specifically tied to users who possess the ability to open cdrom devices, which typically requires either direct device access permissions or specific user group membership that allows such operations.
The operational impact of this vulnerability extends beyond simple service disruption as it represents a potential pathway for privilege escalation or system compromise. While the immediate effect is a denial of service condition that crashes the kernel and requires system reboot, the underlying memory corruption could potentially be exploited further if attackers can leverage additional vulnerabilities or if the system lacks proper kernel security mitigations. The vulnerability is particularly concerning in environments where multiple users share systems or where cdrom access is not properly restricted, as it allows unprivileged users to destabilize critical system operations. From a security perspective, this flaw aligns with CWE-476 which describes NULL pointer dereference conditions, and represents a classic example of how improper variable handling in kernel space can lead to system instability and potential security implications.
The exploitation of CVE-2009-3288 demonstrates the importance of proper input validation and variable management in kernel-level code, particularly within device driver implementations that handle user-supplied data. The fact that this vulnerability can be triggered through legitimate system utilities like xcdroast highlights the need for comprehensive testing and code review processes in kernel development, as well as the necessity of proper access controls for device interfaces. System administrators should ensure that all kernel versions are updated to patched releases that address this specific vulnerability, as the exposure window for this flaw represents a significant risk to system availability and stability. The remediation process involves applying kernel updates that correct the variable reference error in the sg_build_indirect function, ensuring proper memory access patterns and eliminating the potential for NULL pointer dereference conditions that can lead to system crashes and denial of service scenarios.
From an ATT&CK framework perspective, this vulnerability aligns with techniques involving privilege escalation and denial of service operations, though it requires the initial condition of having access to cdrom devices to be exploited effectively. The vulnerability represents a low-barrier attack vector that demonstrates how seemingly minor programming errors in kernel code can have significant operational impacts. Organizations should implement proper system hardening measures including restrictive device access controls and regular kernel updates to mitigate the risk of exploitation. The vulnerability also underscores the importance of kernel security modules and runtime protections that can detect and prevent improper memory access patterns before they can cause system instability. Proper monitoring and alerting systems should be configured to detect kernel oops conditions and system crashes that may indicate exploitation attempts.