CVE-2005-0186 in IOS
Summary
by MITRE
Cisco IOS 12.1YD, 12.2T, 12.3 and 12.3T, when configured for the IOS Telephony Service (ITS), CallManager Express (CME) or Survivable Remote Site Telephony (SRST), allows remote attackers to cause a denial of service (device reboot) via a malformed packet to the SCCP port.
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Analysis
by VulDB Data Team • 07/05/2025
The vulnerability identified as CVE-2005-0186 represents a critical denial of service flaw affecting Cisco IOS versions 12.1YD, 12.2T, 12.3, and 12.3T when configured with IOS Telephony Service ITS, CallManager Express CME, or Survivable Remote Site Telephony SRST functionality. This weakness specifically targets the SCCP protocol implementation within Cisco routers and switches, creating a pathway for remote attackers to disrupt network operations through carefully crafted malformed packets. The vulnerability operates at the network layer where telephony services are integrated into routing infrastructure, making it particularly dangerous for enterprise and service provider networks that rely on integrated voice and data communications.
The technical flaw manifests in the insufficient input validation mechanisms within the SCCP processing code of Cisco IOS. When a malformed packet is received on the SCCP port, the system fails to properly handle the unexpected data structure, leading to a buffer overflow condition or other memory corruption scenarios. This improper handling of malformed input causes the telephony service process to crash and subsequently triggers a complete device reboot. The vulnerability is particularly concerning because SCCP port typically operates on TCP port 2000, and the attack can be executed remotely without requiring authentication credentials, making it accessible to any network entity capable of sending packets to the affected device.
The operational impact of this vulnerability extends beyond simple service disruption, as it can lead to significant business continuity issues for organizations relying on integrated telephony services. Network administrators face the challenge of maintaining availability of voice communications while managing the risk of unexpected device reboots that could occur at any time. The vulnerability affects not only individual devices but can potentially cascade through network infrastructure if multiple telephony-enabled devices are present, creating widespread service degradation. Organizations with distributed networks using SRST capabilities are particularly at risk since these configurations often involve multiple remote sites that could be simultaneously compromised.
Cisco has addressed this vulnerability through software updates and patches that implement proper input validation for SCCP packet processing. Organizations should prioritize applying these security updates to all affected Cisco IOS devices, particularly those configured with telephony services. Network segmentation and access control measures can provide temporary mitigation by restricting access to SCCP ports from untrusted networks. Additionally, monitoring network traffic for anomalous SCCP packet patterns can help detect potential exploitation attempts. This vulnerability aligns with CWE-121, which addresses stack-based buffer overflow conditions, and relates to ATT&CK technique T1499.004 for network denial of service attacks. The flaw demonstrates the importance of secure coding practices in network infrastructure software and highlights the risks associated with protocol implementations that do not adequately validate incoming data, particularly in mission-critical telephony environments where reliability is paramount.