CVE-2009-0631 in IOS
Summary
by MITRE
Unspecified vulnerability in Cisco IOS 12.0 through 12.4, when configured with (1) IP Service Level Agreements (SLAs) Responder, (2) Session Initiation Protocol (SIP), (3) H.323 Annex E Call Signaling Transport, or (4) Media Gateway Control Protocol (MGCP) allows remote attackers to cause a denial of service (blocked input queue on the inbound interface) via a crafted UDP packet.
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Analysis
by VulDB Data Team • 05/09/2025
This vulnerability exists within Cisco IOS versions 12.0 through 12.4 and specifically affects devices configured with certain signaling protocols including IP SLAs Responder, SIP, H.323 Annex E Call Signaling Transport, and MGCP. The flaw manifests as a denial of service condition that occurs when the device processes crafted UDP packets, leading to a blocked input queue on the inbound interface. This represents a critical weakness in the packet processing logic that can be exploited remotely without authentication, making it particularly dangerous in network environments where such protocols are actively utilized. The vulnerability falls under the category of input validation issues and can be classified as a CWE-129 weakness related to insufficient input validation.
The technical exploitation of this vulnerability involves sending specially crafted UDP packets to interfaces configured with the affected protocols. When these malformed packets are received, the IOS processing engine fails to properly handle the packet structure, causing the input queue to become blocked and preventing legitimate traffic from being processed. This creates a denial of service condition that can effectively render network services unavailable to authorized users while maintaining the device's operational status. The vulnerability specifically impacts the packet processing pipeline and can be categorized under ATT&CK technique T1498 related to Network Denial of Service attacks.
Network administrators should implement immediate mitigations including disabling unnecessary protocols on affected interfaces, implementing ingress filtering to block suspicious UDP traffic, and applying Cisco's recommended security patches. The vulnerability demonstrates the importance of proper input validation in network operating systems and highlights the risks associated with complex signaling protocols that must handle various packet formats. Organizations should also consider implementing monitoring solutions to detect anomalous traffic patterns that may indicate exploitation attempts. The impact extends beyond simple service interruption as it can affect business continuity and network reliability, particularly in environments where these protocols are essential for voice and video communications. Regular vulnerability assessments and security updates remain crucial for maintaining network integrity against such exploits.