CVE-2017-12259 in Small Business SPA51x Series IP
Summary
by MITRE
A vulnerability in the implementation of Session Initiation Protocol (SIP) functionality in Cisco Small Business SPA51x Series IP Phones could allow an unauthenticated, remote attacker to cause an affected device to become unresponsive, resulting in a denial of service (DoS) condition. The vulnerability is due to the improper handling of SIP request messages by an affected device. An attacker could exploit this vulnerability by sending malformed SIP messages to an affected device. A successful exploit could allow the attacker to cause the affected device to become unresponsive, resulting in a DoS condition that persists until the device is restarted manually. This vulnerability affects Cisco Small Business SPA51x Series IP Phones that are running Cisco SPA51x Firmware Release 7.6.2SR1 or earlier. Cisco Bug IDs: CSCvc63982.
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Analysis
by VulDB Data Team • 01/19/2021
The vulnerability identified as CVE-2017-12259 represents a critical denial of service weakness within Cisco Small Business SPA51x Series IP Phones, specifically affecting firmware versions 7.6.2SR1 and earlier. This flaw resides in the Session Initiation Protocol implementation that governs how these telephony devices establish, modify, and terminate voice and video communications. The vulnerability stems from inadequate input validation and error handling mechanisms within the SIP message processing subsystem, creating a pathway for malicious actors to disrupt normal device operations without requiring authentication credentials or network access privileges.
The technical exploitation of this vulnerability occurs through the crafting and transmission of malformed SIP request messages to targeted devices. When an affected phone receives these specially crafted packets, the device's SIP processing engine fails to properly handle the unexpected message structures, leading to a system crash or complete hang condition. This improper handling of malformed inputs constitutes a classic buffer overflow or input validation vulnerability pattern that has been documented in various cybersecurity frameworks including CWE-129, which addresses issues related to insufficient input validation. The attack vector is particularly concerning as it operates over the network without requiring any prior authentication, making it accessible to anyone who can reach the device's network interface.
The operational impact of this vulnerability extends beyond simple service disruption, as it can effectively render critical communication infrastructure unusable for extended periods. When an affected device becomes unresponsive, users lose access to voice communication capabilities, potentially impacting business operations, emergency services, or personal communication needs. The persistence of the DoS condition until manual device restart creates a significant operational burden, particularly in environments where multiple devices are affected simultaneously. This vulnerability aligns with ATT&CK technique T1499.004, which covers network denial of service attacks, and demonstrates how weaknesses in communication protocols can be leveraged to create cascading failures in voice infrastructure systems. The affected devices are particularly vulnerable due to their limited security features and the absence of robust input sanitization mechanisms that could otherwise protect against malformed message processing.
Organizations should implement immediate mitigation strategies including firmware updates to versions that address the vulnerability, network segmentation to isolate affected devices, and monitoring for unusual SIP traffic patterns that might indicate exploitation attempts. Cisco released firmware updates to resolve this issue, and administrators should ensure all affected devices are upgraded to the latest secure firmware versions. Network-based intrusion detection systems can be configured to monitor for suspicious SIP message patterns, while regular security assessments should be conducted to identify and remediate similar vulnerabilities across the entire telephony infrastructure. The vulnerability also highlights the importance of secure coding practices and comprehensive input validation in embedded communication devices, emphasizing the need for robust error handling mechanisms that prevent malformed inputs from causing system failures.