CVE-2017-6630 in IP Phone 8851
Summary
by MITRE
A vulnerability in the Session Initiation Protocol (SIP) implementation of Cisco IP Phone 8851 11.0(0.1) could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition. The vulnerability is due to an abnormal SIP message. An attacker could exploit this vulnerability by manipulating the CANCEL packet. An exploit could allow the attacker to cause a disruption of service to the phone. Cisco Bug IDs: CSCvc34795.
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Analysis
by VulDB Data Team • 12/25/2020
The vulnerability identified as CVE-2017-6630 affects Cisco IP Phone 8851 running software version 11.0(0.1) and represents a significant denial of service weakness within the Session Initiation Protocol implementation. This flaw resides in the phone's handling of SIP messages, specifically targeting the CANCEL packet mechanism that is fundamental to SIP protocol operations for terminating ongoing sessions. The vulnerability stems from insufficient input validation and error handling within the SIP message processing engine, creating an exploitable condition that can be triggered remotely without authentication requirements.
The technical exploitation of this vulnerability occurs through manipulation of the CANCEL packet format which is used in SIP to cancel outstanding requests. When an attacker crafts a malformed or specially constructed CANCEL message, the phone's SIP implementation fails to properly process the packet, leading to a system crash or reboot. This behavior aligns with CWE-121, which describes heap-based buffer overflow conditions, and represents a classic example of improper input validation where the system does not adequately sanitize incoming SIP messages before processing them. The vulnerability operates at the application layer of the network stack and specifically targets the SIP stack implementation within the phone's firmware.
The operational impact of this vulnerability extends beyond simple service disruption as it can render the affected Cisco IP Phone completely inoperable, effectively removing a critical communication endpoint from the network. This disruption can have cascading effects in enterprise environments where these phones serve as primary communication devices for employees, potentially affecting business continuity and emergency communication systems. The remote nature of the exploit means that attackers can trigger the DoS condition from outside the network perimeter, making it particularly dangerous for organizations that do not properly segment their voice communication networks from general network traffic. This vulnerability directly maps to ATT&CK technique T1499.004, which covers network denial of service attacks, and represents a significant risk to voice over IP infrastructure security.
Organizations should implement immediate mitigations including applying the relevant Cisco security patches and updates that address the SIP message handling flaws in the affected firmware versions. Network segmentation strategies should be employed to isolate voice communication systems from general network traffic, and monitoring should be implemented to detect anomalous SIP message patterns that might indicate exploitation attempts. Additionally, implementing access controls and authentication mechanisms for SIP signaling can provide additional defense in depth. The vulnerability highlights the importance of maintaining current firmware versions and conducting regular security assessments of voice communication infrastructure, as it demonstrates how seemingly minor protocol implementation flaws can result in complete service outages. Cisco's advisory CSCvc34795 provides specific guidance on the patched versions and recommended remediation steps that organizations should implement immediately to protect their network infrastructure from this and similar vulnerabilities.