CVE-2012-4435 in fwknop
Summary
by MITRE
fwknop before 2.0.3 does not properly validate IP addresses, which allows remote authenticated users to cause a denial of service (server crash) via a long IP address.
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Analysis
by VulDB Data Team • 12/19/2021
The vulnerability identified as CVE-2012-4435 affects fwknop versions prior to 2.0.3 and represents a critical flaw in the application's input validation mechanisms. This issue stems from inadequate sanitization of IP address parameters within the software's processing pipeline, creating an avenue for malicious actors to exploit the system's memory handling capabilities. The vulnerability specifically targets the server-side processing logic where IP addresses are parsed and validated, allowing attackers to craft malicious inputs that exceed normal parameter boundaries.
The technical implementation of this vulnerability resides in the software's failure to enforce proper bounds checking on IP address length during the authentication process. When fwknop receives an authenticated request containing an excessively long IP address, the application's internal buffer management fails to handle the overflow gracefully, resulting in memory corruption and subsequent application termination. This behavior manifests as a denial of service condition where the server crashes and becomes unavailable to legitimate users. The flaw operates at the application layer and can be triggered through authenticated network connections, making it particularly concerning for systems that rely on fwknop for network access control.
From an operational perspective, this vulnerability creates significant risk for organizations using fwknop as part of their network security infrastructure. The remote authenticated nature of the exploit means that attackers who have already gained access to the system through other means can leverage this flaw to disrupt services and potentially escalate their compromise. The impact extends beyond simple service disruption as the server crash can result in loss of network access for legitimate users and may provide attackers with additional opportunities to maintain persistence or conduct further reconnaissance. The vulnerability affects systems where fwknop serves as a gateway protection mechanism, potentially compromising the entire access control framework.
Security practitioners should prioritize immediate patching of affected systems to address this vulnerability, as the remediation requires updating to fwknop version 2.0.3 or later where proper input validation has been implemented. The fix addresses the underlying issue by introducing comprehensive bounds checking and input sanitization mechanisms that prevent buffer overflows during IP address processing. Organizations should also implement network monitoring to detect anomalous authentication patterns that might indicate exploitation attempts, while maintaining strict access controls to limit the attack surface. This vulnerability aligns with CWE-122, which describes improper restriction of operations within a limited error handling scope, and may be categorized under ATT&CK technique T1499 for network disruption. The implementation of defensive measures should include regular security assessments of network access control systems and maintaining updated threat intelligence to identify similar vulnerabilities in related software components.