CVE-2006-5153 in Personal Firewall
Summary
by MITRE
The (1) fwdrv.sys and (2) khips.sys drivers in Sunbelt Kerio Personal Firewall 4.3.268 and earlier do not validate arguments passed through to SSDT functions, including NtCreateFile, NtDeleteFile, NtLoadDriver, NtMapViewOfSection, NtOpenFile, and NtSetInformationFile, which allows local users to cause a denial of service (crash) and possibly other impacts via unspecified vectors.
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Analysis
by VulDB Data Team • 04/23/2026
The vulnerability identified in CVE-2006-5153 affects the Sunbelt Kerio Personal Firewall version 4.3.268 and earlier, specifically targeting two kernel-mode drivers named fwdrv.sys and khips.sys. These drivers operate within the Windows kernel space and interact with the System Service Descriptor Table (SSDT) to handle various system calls. The flaw stems from inadequate input validation within these drivers when processing arguments passed through SSDT functions, creating a critical security weakness that can be exploited by local attackers. This vulnerability represents a classic case of insufficient validation in kernel-mode components, where the drivers fail to properly sanitize or verify parameters before executing system-level operations.
The technical implementation of this vulnerability involves the drivers' failure to validate arguments passed to essential SSDT functions such as NtCreateFile, NtDeleteFile, NtLoadDriver, NtMapViewOfSection, NtOpenFile, and NtSetInformationFile. When these functions receive malformed or unexpected parameters, the drivers lack proper validation mechanisms to detect and reject potentially harmful inputs. This absence of input sanitization creates multiple attack vectors that can trigger system instability, as the kernel-mode code executes without proper parameter checking. The vulnerability manifests as a denial of service condition, causing system crashes or blue screen errors, but potentially could enable more severe impacts including privilege escalation or arbitrary code execution depending on the specific exploitation vectors.
From an operational perspective, this vulnerability poses significant risks to systems running the affected Kerio Personal Firewall version, as local users with minimal privileges can leverage this flaw to disrupt system operations. The impact extends beyond simple service interruption since kernel-mode exploitation can compromise the entire system stability and potentially provide attackers with elevated privileges. The vulnerability's classification aligns with CWE-707, which addresses improper neutralization of special elements in output used by a downstream component, and more specifically with CWE-254, addressing security weaknesses in the kernel. According to ATT&CK framework, this vulnerability maps to T1068, which covers 'Exploitation for Privilege Escalation' and T1499, covering 'Endpoint Denial of Service', with potential for lateral movement and system compromise.
Mitigation strategies for this vulnerability should prioritize immediate patching of the affected Kerio Personal Firewall software to version 4.3.269 or later, which contains the necessary fixes for input validation. System administrators should implement additional security measures including disabling unnecessary kernel-mode drivers, applying the principle of least privilege, and monitoring for unusual system behavior or kernel crashes. Network segmentation and endpoint protection solutions can provide additional layers of defense against exploitation attempts. The vulnerability highlights the critical importance of proper input validation in kernel-mode components and demonstrates how insufficient security controls in device drivers can create significant attack surfaces. Organizations should conduct thorough vulnerability assessments of their endpoint security solutions and ensure that all kernel-mode components undergo rigorous security testing before deployment. The remediation process should include verification of driver integrity and monitoring of system logs for potential exploitation attempts, as the vulnerability's impact can be subtle and may not always result in immediate system crashes but could enable more sophisticated attacks over time.