CVE-2009-4049 in Avast Antivirus Home
Summary
by MITRE
Heap-based buffer overflow in aswRdr.sys (aka the TDI RDR driver) in avast! Home and Professional 4.8.1356.0 allows local users to cause a denial of service (memory corruption) or possibly gain privileges via crafted arguments to IOCTL 0x80002024.
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Analysis
by VulDB Data Team • 10/20/2025
The vulnerability identified as CVE-2009-4049 represents a critical heap-based buffer overflow within the aswRdr.sys driver component of avast! Home and Professional version 4.8.1356.0. This driver serves as the TDI RDR (Transport Driver Interface Redirector) component that handles network file redirection operations within the antivirus software's kernel-mode architecture. The flaw specifically manifests when processing IOCTL (Input/Output Control) requests with code 0x80002024, which indicates a potential security risk that could be exploited by local attackers to manipulate the driver's memory management functions.
The technical implementation of this vulnerability stems from inadequate bounds checking within the driver's handling of user-supplied input parameters. When the aswRdr.sys driver receives the crafted IOCTL 0x80002024 request, it fails to properly validate the size or content of the input buffer before attempting to copy data into heap-allocated memory regions. This oversight creates a condition where malicious input can overwrite adjacent memory locations, potentially corrupting heap metadata or overwriting critical driver structures. The heap-based nature of the overflow means that the vulnerability affects the dynamic memory allocation system rather than stack-based buffers, making it particularly challenging to predict and exploit consistently.
From an operational perspective, this vulnerability presents dual threat vectors that significantly impact system security and stability. Local attackers can leverage this flaw to achieve either a denial of service condition through memory corruption that crashes the driver or potentially escalate privileges to kernel mode execution. The privilege escalation aspect is particularly concerning as it could allow attackers to bypass standard user permissions and execute arbitrary code with system-level privileges, effectively compromising the entire system. The vulnerability's local nature means that exploitation requires physical access or existing user-level access, but once exploited, the impact extends to full system compromise.
The mitigation strategies for CVE-2009-4049 should focus on immediate software updates and system hardening measures. The primary solution involves upgrading to a patched version of avast! Home and Professional that addresses the buffer overflow in the aswRdr.sys driver. Organizations should also implement kernel-mode exploit mitigation techniques such as Data Execution Prevention (DEP) and Address Space Layout Randomization (ASLR) to reduce exploit reliability. System administrators should consider disabling unnecessary driver functionality and implementing strict access controls for the affected driver components. Additionally, monitoring for abnormal driver behavior and implementing intrusion detection systems can help identify potential exploitation attempts. This vulnerability aligns with CWE-121, heap-based buffer overflow, and represents a typical attack vector categorized under ATT&CK technique T1068, Exploitation for Privilege Escalation, highlighting the critical importance of kernel-mode security in endpoint protection software.
The broader implications of this vulnerability demonstrate the inherent risks associated with complex kernel-mode drivers in security software. Antivirus vendors must implement rigorous input validation and memory management practices in their kernel components to prevent such flaws from being exploited. The vulnerability also underscores the importance of proper code review and security testing for all driver components, as these elements operate with the highest system privileges and present significant attack surfaces for sophisticated adversaries.