CVE-2009-1929 in Windows
Summary
by MITRE
Heap-based buffer overflow in the Microsoft Terminal Services Client ActiveX control running RDP 6.1 on Windows XP SP2, Vista SP1 or SP2, or Server 2008 Gold or SP2; or 5.2 or 6.1 on Windows XP SP3; allows remote attackers to execute arbitrary code via unspecified parameters to unknown methods, aka "Remote Desktop Connection ActiveX Control Heap Overflow Vulnerability."
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Analysis
by VulDB Data Team • 09/18/2018
The vulnerability identified as CVE-2009-1929 represents a critical heap-based buffer overflow within the Microsoft Terminal Services Client ActiveX control that operates with Remote Desktop Protocol version 6.1. This flaw specifically affects systems running Windows XP Service Pack 2 and 3, Windows Vista Service Pack 1 and 2, and Windows Server 2008 in various configurations. The vulnerability stems from improper input validation within the ActiveX control's method handling mechanisms, creating a condition where maliciously crafted parameters can overflow allocated heap memory buffers. The affected ActiveX control is part of the Remote Desktop Connection functionality that enables remote desktop sessions, making this vulnerability particularly dangerous as it can be exploited through web-based attacks when users visit malicious websites or open infected email attachments. This vulnerability falls under the CWE-121 heap-based buffer overflow category, which is classified as a fundamental memory safety issue that can lead to arbitrary code execution. The attack vector leverages the ActiveX control's interaction with web browsers, specifically targeting the way the control processes method parameters that are passed through web pages or web-based RDP connections. The vulnerability is particularly concerning because it allows remote attackers to execute arbitrary code with the privileges of the user running the affected ActiveX control, potentially leading to full system compromise.
The technical exploitation of this vulnerability occurs when the malicious ActiveX control receives specially crafted parameters through unknown methods that trigger the buffer overflow condition in the heap memory allocation. The heap overflow specifically affects the memory management structures within the Terminal Services Client component, where insufficient bounds checking allows data to overwrite adjacent memory locations. Attackers can manipulate the control's behavior by passing malicious inputs that cause the heap allocator to write beyond the intended buffer boundaries, potentially overwriting critical memory structures such as function pointers or return addresses. This type of vulnerability is particularly dangerous because it can be triggered through web browsing activities, making it an attractive target for drive-by download attacks where users are compromised simply by visiting malicious websites. The vulnerability's impact is amplified by the widespread deployment of Windows XP and Vista systems at the time of disclosure, as these operating systems were still prevalent in enterprise and consumer environments. The exploitation process typically involves crafting a malicious web page that loads the vulnerable ActiveX control and passes malicious parameters through method calls, causing the buffer overflow to occur in the heap memory space.
The operational impact of CVE-2009-1929 extends beyond simple code execution, as successful exploitation can lead to complete system compromise and persistent backdoor access. When an attacker successfully exploits this vulnerability, they gain the ability to execute arbitrary code within the context of the user's session, which can include elevated privileges if the user has administrative rights. The vulnerability's nature means that it can be exploited remotely without requiring authentication, making it particularly dangerous for enterprise environments where users may inadvertently visit malicious websites or receive infected email attachments. The exploitation process can result in privilege escalation, data theft, system monitoring, and the installation of additional malware. Organizations running affected systems are particularly vulnerable as this vulnerability can be exploited through web browsing activities, making it difficult to prevent through traditional network security measures. The vulnerability also has implications for security compliance and regulatory requirements, as it represents a significant exposure that could lead to data breaches and system compromise. The widespread use of Windows XP and Vista systems at the time of disclosure meant that many organizations were potentially exposed to this vulnerability without adequate protection mechanisms in place.
Mitigation strategies for CVE-2009-1929 require a multi-layered approach that addresses both immediate protection and long-term system hardening. The most effective immediate solution involves disabling the vulnerable ActiveX control through Group Policy settings or registry modifications, preventing automatic execution of the control in web browsers. Microsoft released security updates that patched the vulnerability in their security bulletin MS09-021, which should be deployed immediately across all affected systems. Organizations should also implement browser security measures such as disabling ActiveX controls in Internet Explorer, particularly for untrusted websites, and implementing application whitelisting policies that restrict execution of unsigned or untrusted ActiveX controls. Network-level protections such as firewall rules and intrusion detection systems can help detect and block exploitation attempts, while security awareness training can reduce the risk of users inadvertently triggering the vulnerability through malicious web content. The vulnerability also highlights the importance of regular patch management and system updates, as this flaw existed in widely deployed systems for an extended period before the patch was released. Organizations should also consider implementing additional security controls such as sandboxing for web browsing activities, network segmentation to limit the potential impact of successful exploitation, and regular vulnerability assessments to identify similar issues in other components of their IT infrastructure. The remediation process should include comprehensive testing of patches in controlled environments to ensure compatibility with existing business applications that may depend on the vulnerable ActiveX control functionality.