CVE-2009-3523 in Antivirus Professional
Summary
by MITRE
aavmKer4.sys in avast! Home and Professional for Windows before 4.8.1356 does not properly validate input to IOCTLs (1) 0xb2d6000c and (2) 0xb2d60034, which allows local users to gain privileges via IOCTL requests using crafted kernel addresses that trigger memory corruption, a different vulnerability than CVE-2008-1625.
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Analysis
by VulDB Data Team • 10/20/2025
The vulnerability identified as CVE-2009-3523 affects avast! Home and Professional versions prior to 4.8.1356 on Windows systems, specifically targeting the aavmKer4.sys kernel driver component. This represents a critical privilege escalation flaw that exploits improper input validation within two specific IOCTL (Input/Output Control) interface functions identified by the codes 0xb2d6000c and 0xb2d60034. The vulnerability falls under the CWE-121 category of stack-based buffer overflow, though it manifests as a more complex kernel-level memory corruption issue that enables local attackers to elevate their system privileges from standard user level to kernel-level access. The flaw exists in the driver's handling of user-supplied data without adequate validation, creating a pathway for malicious input to corrupt kernel memory structures.
The technical exploitation of this vulnerability occurs through crafted IOCTL requests that target the vulnerable kernel addresses within the aavmKer4.sys driver. When local users submit specially crafted input parameters to these specific IOCTL interfaces, the driver fails to properly validate the supplied data structures, leading to memory corruption that can be leveraged to execute arbitrary code with kernel privileges. This type of vulnerability represents a classic kernel-mode exploit vector that aligns with ATT&CK technique T1068, which covers "Exploitation for Privilege Escalation." The memory corruption typically manifests as overwrite of critical kernel data structures or function pointers, potentially allowing attackers to redirect execution flow or manipulate kernel objects. The vulnerability is particularly concerning because it requires no special privileges to initiate the exploit, making it accessible to any local user with access to the system.
The operational impact of CVE-2009-3523 extends beyond simple privilege escalation, as successful exploitation can provide attackers with complete control over the affected system. Once elevated to kernel privileges, attackers can bypass all operating system security mechanisms, including user access controls, file system protections, and other security features. The vulnerability allows for persistent backdoor installation, system monitoring, data exfiltration, and complete system compromise. This represents a significant risk to enterprise environments where avast! antivirus software is deployed, as it could enable attackers to establish long-term access to systems without detection. The fact that this vulnerability differs from CVE-2008-1625 indicates it represents a distinct attack surface within the same product line, suggesting potential code reuse or similar architectural flaws that may exist in other components. Organizations should consider this vulnerability as part of a broader exploitation strategy that could lead to complete system compromise.
Mitigation strategies for CVE-2009-3523 focus primarily on immediate software updates and system hardening measures. The most effective solution involves upgrading to avast! Home and Professional version 4.8.1356 or later, which includes proper input validation and memory safety improvements in the affected kernel driver. System administrators should also implement additional security controls such as kernel patch protection, driver signature enforcement, and restricted user access to prevent exploitation attempts. The vulnerability highlights the importance of kernel-mode security and proper IOCTL parameter validation, which aligns with security frameworks emphasizing defense in depth and principle of least privilege. Organizations should conduct comprehensive vulnerability assessments to identify other potentially vulnerable kernel components and ensure that all security patches are applied promptly. This vulnerability serves as a reminder of the critical importance of secure coding practices in kernel drivers and the potential consequences of inadequate input validation in privileged code execution environments.