CVE-2007-0431 in Fritzbox
Summary
by MITRE
AVM Fritz!Box 7050, and possibly other product models, allows remote attackers to cause a denial of service (VoIP application crash) via a zero-length UDP packet to the SIP port (port 5060).
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Analysis
by VulDB Data Team • 08/01/2019
The vulnerability identified as CVE-2007-0431 affects AVM FritzBox product line. This issue represents a significant security weakness in the router's handling of Session Initiation Protocol (SIP) traffic, which is fundamental to Voice over Internet Protocol communications. The vulnerability specifically targets the SIP port 5060, which serves as the standard port for SIP signaling in VoIP applications, making it a critical component of the router's telephony functionality.
The technical flaw manifests when the affected router receives a zero-length UDP packet directed at the SIP port 5060. This seemingly innocuous packet triggers a buffer overflow or memory corruption condition within the router's VoIP application processing mechanism. The zero-length packet bypasses normal packet validation procedures and causes the application to crash or become unresponsive. The vulnerability stems from inadequate input validation and error handling within the router's SIP implementation, which fails to properly handle malformed or unexpected packet structures. This type of vulnerability aligns with CWE-129, which addresses improper validation of length of input buffers, and CWE-121, concerning stack-based buffer overflow conditions.
The operational impact of this vulnerability extends beyond simple service disruption, as it can be exploited by remote attackers to systematically disable VoIP services on affected networks. This denial of service attack can render the entire VoIP infrastructure unusable, affecting business communications, emergency services, and personal telephony capabilities. The remote nature of the attack means that threat actors can exploit this vulnerability from outside the network perimeter, without requiring physical access or authentication credentials. The attack vector is particularly concerning because it leverages the standard SIP port, making it difficult to distinguish from legitimate traffic and potentially allowing attackers to maintain persistent disruption of services.
Network administrators and security professionals should implement immediate mitigations to address this vulnerability. The most effective approach involves configuring firewall rules to block incoming UDP traffic on port 5060 from untrusted networks, while ensuring that legitimate VoIP traffic can still function properly. Additionally, network segmentation should be implemented to isolate VoIP traffic from general network access. The vulnerability demonstrates the importance of proper input validation and error handling in network infrastructure devices, as outlined in the ATT&CK framework's network infrastructure tactics. Organizations should also consider implementing intrusion detection systems capable of identifying anomalous SIP traffic patterns and zero-length packet deliveries. Regular firmware updates and security patches should be applied to address known vulnerabilities, while network monitoring should include specific detection capabilities for this type of denial of service attack. The incident highlights the critical need for robust security testing of network infrastructure devices, particularly those handling real-time communication protocols that are essential to business operations and emergency services.