CVE-2006-3973 in My Firewall Plus
Summary
by MITRE
My Firewall Plus 5.0 Build 1119 does not verify if explorer.exe is running before launching iexplore.exe from the "Test Your Firewall" feature, which allows local users to gain SYSTEM privileges.
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Analysis
by VulDB Data Team • 04/28/2026
The vulnerability identified in CVE-2006-3973 resides within My Firewall Plus version 5.0 Build 1119, a network security application designed to protect systems through firewall management. This flaw represents a critical privilege escalation vulnerability that exploits the application's improper validation of system processes before executing web browser components. The vulnerability specifically manifests in the "Test Your Firewall" feature, which is intended as a diagnostic tool to verify firewall configurations but becomes a vector for unauthorized system access due to its flawed execution logic.
The technical flaw occurs when the application attempts to launch Internet Explorer through iexplore.exe without first confirming whether the Windows Explorer process is actively running. This oversight creates a dangerous execution environment where local users can manipulate the system's process hierarchy to execute code with elevated privileges. The vulnerability stems from a lack of proper process validation and privilege checking mechanisms within the application's code execution flow, allowing attackers to exploit the absence of verification steps that should occur before launching system-critical processes.
From an operational standpoint, this vulnerability presents a severe security risk as it enables local users to escalate their privileges to the SYSTEM level without requiring administrative credentials or complex exploitation techniques. The attack vector is relatively straightforward since it only requires local system access and the ability to interact with the My Firewall Plus application interface. Once exploited, the vulnerability provides attackers with complete control over the target system, including the ability to modify system files, install malware, and access sensitive data. This privilege escalation capability makes the vulnerability particularly dangerous in environments where multiple users share the same system or where unprivileged accounts exist.
The vulnerability aligns with CWE-787, which addresses out-of-bounds writes and related memory corruption issues, though in this case the flaw manifests through improper process validation rather than memory corruption. From an adversarial perspective, this vulnerability maps to several ATT&CK tactics including privilege escalation and defense evasion, as attackers can leverage this weakness to gain system-level access and potentially hide their activities within the compromised system. The exploitability factor is enhanced by the fact that it requires minimal technical expertise to execute, making it attractive to both skilled attackers and less sophisticated threat actors.
Mitigation strategies should focus on immediate patching of the My Firewall Plus application to version 5.0 Build 1120 or later, which contains the necessary fixes for the process validation flaw. System administrators should also implement least privilege principles, ensuring that local user accounts have minimal necessary permissions and that the application is run with appropriate security contexts. Additional protective measures include monitoring for unauthorized execution of iexplore.exe processes and implementing application control policies that restrict the execution of potentially dangerous process combinations. Regular security assessments should verify that similar process validation flaws do not exist in other applications within the organization's attack surface, as this vulnerability demonstrates how seemingly benign features can become critical security weaknesses when proper validation mechanisms are omitted.