CVE-2009-2918 in VPN Client
Summary
by MITRE
The tgbvpn.sys driver in TheGreenBow IPSec VPN Client 4.61.003 allows local users to cause a denial of service (NULL pointer dereference and system crash) via a crafted request to the 0x80000034 IOCTL, probably involving an input or output buffer size of 0.
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Analysis
by VulDB Data Team • 10/10/2025
The vulnerability described in CVE-2009-2918 resides within the tgbvpn.sys kernel driver component of TheGreenBow IPSec VPN Client version 4.61.003, representing a critical security flaw that enables local privilege escalation through a denial of service condition. This issue manifests as a NULL pointer dereference when processing a specific IOCTL (Input/Output Control) request with the code 0x80000034, which is typically used for communication between user-mode applications and kernel-mode drivers in Windows operating systems. The flaw occurs when the driver receives a crafted request with either an input or output buffer size set to zero, creating a scenario where the kernel driver attempts to dereference a NULL pointer, leading to an immediate system crash and potential denial of service for legitimate users.
The technical nature of this vulnerability aligns with CWE-476, which specifically addresses NULL pointer dereference conditions in software implementations, making it particularly dangerous as it can be exploited by any local user with access to the system. When the kernel driver processes the malformed IOCTL request, it fails to properly validate the buffer size parameters before attempting to access memory locations, resulting in an unhandled exception that crashes the entire operating system kernel. This type of vulnerability represents a fundamental failure in input validation and memory management practices within kernel-mode drivers, which are expected to handle all possible input scenarios gracefully without compromising system stability. The attack vector is particularly concerning because it requires no elevated privileges to execute, as local users can trigger the vulnerability through normal application usage patterns.
The operational impact of this vulnerability extends beyond simple service disruption, as it can be leveraged to create persistent denial of service conditions that may be difficult to detect and remediate. System administrators and security teams face the challenge of identifying when such attacks occur, particularly since the crash may not be immediately attributed to a specific driver component. The vulnerability affects systems running TheGreenBow IPSec VPN Client, potentially impacting organizations that rely on this specific VPN solution for remote access, making it a significant concern for enterprise security. From an adversarial perspective, this vulnerability maps to ATT&CK technique T1499.004, which involves network disruption through denial of service attacks, though in this case the disruption occurs at the kernel level rather than at the network layer.
Mitigation strategies for this vulnerability should focus on immediate driver updates from TheGreenBow vendor to address the NULL pointer dereference issue, as well as implementing comprehensive input validation mechanisms within the driver code to prevent malformed IOCTL requests from reaching the problematic code paths. System administrators should consider disabling unnecessary kernel driver functionalities and implementing monitoring solutions that can detect abnormal driver behavior patterns. The vulnerability also highlights the importance of kernel-mode driver security reviews and adherence to secure coding practices that prevent NULL pointer dereferences, particularly in components that handle user-supplied data through IOCTL interfaces. Organizations should also implement regular security assessments of third-party VPN clients to identify similar vulnerabilities that may exist in other network security components, as this represents a pattern of inadequate input validation in kernel drivers that could affect other similar products in the market.