CVE-2007-2903 in Office
Summary
by MITRE
Buffer overflow in the HelpPopup method in the Microsoft Office 2000 Controllo UA di Microsoft Office ActiveX control (OUACTRL.OCX) 1.0.1.9 allows remote attackers to cause a denial of service (probably winhlp32.exe crash) via a long first argument. NOTE: it is not clear whether this issue crosses privilege boundaries.
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Analysis
by VulDB Data Team • 06/08/2025
The vulnerability identified as CVE-2007-2903 represents a critical buffer overflow flaw within the Microsoft Office 2000 Controllo UA ActiveX control component. This specific vulnerability resides in the HelpPopup method of the OUACTRL.OCX ActiveX control version 1.0.1.9, which is part of the broader Microsoft Office suite ecosystem. The flaw manifests when the control processes a malformed first argument parameter, creating a condition where memory allocation exceeds the intended buffer boundaries. This type of vulnerability falls under the CWE-121 category of stack-based buffer overflow, where insufficient bounds checking allows attackers to overwrite adjacent memory locations.
The technical exploitation of this vulnerability occurs through the manipulation of the HelpPopup method within the ActiveX control, which is designed to provide contextual help functionality. When a remote attacker supplies an excessively long string as the first argument parameter, the control fails to properly validate input length before copying data into a fixed-size buffer. This allows the attacker to overwrite adjacent memory regions, potentially leading to arbitrary code execution or system instability. The vulnerability specifically affects the winhlp32.exe process which is responsible for displaying help files in older Microsoft Office versions, making it a prime target for denial of service attacks that can crash the help system and potentially the entire application.
The operational impact of this vulnerability extends beyond simple denial of service, as it can be leveraged to compromise system integrity and availability. The attack vector is particularly concerning because it can be triggered remotely through web-based attacks, where malicious web pages or documents containing the vulnerable ActiveX control can automatically execute the exploit when viewed in Internet Explorer or other browsers that support ActiveX controls. This vulnerability represents a significant risk to organizations using legacy Microsoft Office 2000 systems, as it can be exploited without requiring local system access or elevated privileges. The potential for privilege escalation remains unclear, but the possibility of crossing privilege boundaries makes this vulnerability particularly dangerous in enterprise environments.
Mitigation strategies for this vulnerability should focus on immediate patching and system hardening measures. Microsoft released security updates to address this specific buffer overflow issue, and organizations should prioritize applying these patches to all affected systems. Additionally, administrators should implement browser security policies that disable ActiveX controls or restrict their execution to trusted sites only. The implementation of application whitelisting and sandboxing techniques can further reduce the attack surface by preventing unauthorized ActiveX control execution. Network-based protections such as intrusion prevention systems and web application firewalls should also be configured to detect and block malicious input patterns targeting this vulnerability. From a defensive perspective, this vulnerability aligns with ATT&CK technique T1203 which involves exploitation of software vulnerabilities for privilege escalation, and T1059 which covers the use of command and scripting interpreters. The vulnerability demonstrates how legacy components in enterprise software ecosystems can pose significant security risks, particularly when they lack proper input validation and memory management controls. Organizations should conduct comprehensive vulnerability assessments to identify other potentially vulnerable ActiveX controls and ensure proper security controls are in place to prevent similar issues from compromising system availability and integrity.