CVE-2018-6525 in AVS
Summary
by MITRE
In nProtect AVS V4.0 4.0.0.38, the driver file (TKFsAv.SYS) allows local users to cause a denial of service (BSOD) or possibly have unspecified other impact because of not validating input values from IOCtl 0x220458.
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Analysis
by VulDB Data Team • 01/01/2020
The vulnerability identified as CVE-2018-6525 affects nProtect AVS V4.0 version 4.0.0.38 and represents a critical security flaw within the kernel-mode driver component TKFsAv.SYS. This driver serves as the core protective mechanism for the antivirus software, handling system-level operations and direct hardware interactions. The flaw manifests through improper input validation during processing of IOCTL (Input/Output Control) requests, specifically targeting the control code 0x220458 which is used for communication between user-mode applications and the kernel-mode driver. The lack of proper validation creates a pathway for malicious input manipulation that can be exploited by local attackers with minimal privileges.
The technical implementation of this vulnerability stems from the driver's failure to validate input parameters received through the specified IOCTL interface. When user-mode processes send control codes to the kernel driver, the system expects certain data formats and ranges to maintain system stability and security. However, the TKFsAv.SYS driver does not perform adequate checks on the incoming data, allowing malformed or unexpected values to be processed directly within kernel space. This represents a classic example of buffer over-read or improper input validation, which can lead to unpredictable behavior and system instability. The vulnerability specifically aligns with CWE-129, which describes improper validation of input ranges, and CWE-755, which addresses improper handling of exceptional conditions.
The operational impact of this vulnerability extends beyond simple denial of service conditions, though that represents the most immediate risk. Local users can potentially trigger a Blue Screen of Death (BSOD) by sending crafted input through the IOCTL interface, effectively crashing the operating system and rendering it unusable until manual reboot. However, the unspecified other impacts mentioned in the CVE description suggest that more severe consequences may be possible, including privilege escalation or arbitrary code execution. This aligns with ATT&CK technique T1068, which covers local privilege escalation, and T1059, which addresses command and scripting interpreters. The vulnerability essentially allows an attacker to manipulate kernel-level processes through controlled input, potentially leading to complete system compromise.
Mitigation strategies for this vulnerability should focus on both immediate remediation and long-term architectural improvements. The primary solution involves updating to a patched version of nProtect AVS that properly validates all input parameters received through IOCTL interfaces. System administrators should also implement monitoring solutions to detect unusual patterns of IOCTL usage that might indicate exploitation attempts. Additionally, the principle of least privilege should be enforced, limiting the execution of antivirus driver components to only necessary processes. Organizations should consider implementing kernel-mode driver isolation techniques and regular security assessments of driver components to identify similar validation flaws. The vulnerability demonstrates the critical importance of proper input validation in kernel-space code and highlights the need for comprehensive security testing of all system-level components, particularly those with direct hardware access capabilities that can affect overall system integrity.