CVE-1999-0917 in Internet Explorer
Summary
by MITRE
The Preloader ActiveX control used by Internet Explorer allows remote attackers to read arbitrary files.
VulDB is the best source for vulnerability data and more expert information about this specific topic.
Analysis
by VulDB Data Team • 04/19/2026
The vulnerability described in CVE-1999-0917 represents a critical security flaw in the Preloader ActiveX control that was widely integrated into Internet Explorer browsers during the late 1990s era. This particular vulnerability falls under the category of insecure direct object reference issues and demonstrates how ActiveX controls could be exploited to bypass normal file system access controls. The Preloader ActiveX control was designed to facilitate media loading and playback functionalities within web browsers, but its implementation contained a fundamental security flaw that allowed malicious actors to manipulate file access parameters and retrieve unauthorized data from the target system.
The technical exploitation of this vulnerability occurs through the manipulation of the ActiveX control's file reading capabilities, which were not properly validated or restricted. When Internet Explorer loaded a web page containing malicious code that interacted with the Preloader control, attackers could leverage the control's functionality to access files that should have been protected by standard operating system permissions. This flaw essentially allowed attackers to bypass the normal security boundaries that typically prevent web-based applications from accessing arbitrary files on a user's system. The vulnerability was particularly dangerous because it could be triggered through simple web page loading without requiring any special user interaction or privilege escalation.
The operational impact of this vulnerability was significant for users of Internet Explorer during the period when this control was prevalent. Attackers could potentially access sensitive files including configuration data, user credentials, system logs, and other confidential information stored on the local file system. This capability extended beyond simple information disclosure to potentially enable more sophisticated attacks such as privilege escalation or system compromise. The vulnerability was especially concerning because it could be exploited through social engineering techniques, where users would be unknowingly directed to malicious websites that contained the exploit code. The widespread adoption of Internet Explorer at the time meant that this vulnerability could affect a large number of users across various environments including corporate networks and personal computers.
Organizations and security professionals should have implemented several mitigation strategies to address this vulnerability. The most effective immediate solution was to disable ActiveX controls or remove the vulnerable Preloader control from affected systems. System administrators needed to ensure that users were not exposed to potentially malicious web content and that appropriate network segmentation was in place to limit the potential damage from such exploits. This vulnerability highlighted the broader security challenges associated with ActiveX controls and contributed to the industry's eventual shift toward more secure web technologies. The incident also reinforced the importance of proper input validation and the principle of least privilege in software design, principles that are now fundamental to modern cybersecurity practices and align with the guidance provided in the CWE database for preventing insecure direct object references.
The vulnerability demonstrates how legacy software components can introduce persistent security risks when proper security testing and validation are not performed during development. It also illustrates the challenges that organizations faced during the transition period when web browsers were incorporating increasingly complex ActiveX-based functionality while maintaining backward compatibility with existing applications. This particular case study became important for understanding how seemingly minor implementation flaws in browser components could lead to significant security breaches and contributed to the evolution of more robust security models in web browsers and operating systems. The vulnerability's characteristics align with ATT&CK techniques related to privilege escalation and credential access, making it a relevant example for understanding how initial access through web-based exploits can be leveraged for more comprehensive system compromise.