CVE-2017-12328 in IP Phone 8800
Summary
by MITRE
A vulnerability in Session Initiation Protocol (SIP) call handling in Cisco IP Phone 8800 Series devices could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition because the SIP process unexpectedly restarts. All active phone calls are dropped as the SIP process restarts. The vulnerability is due to incomplete input validation of the SIP packet header. An attacker could exploit this vulnerability by sending a malformed SIP packet to a targeted phone. An exploit could allow the attacker to cause a DoS condition because all phone calls are dropped when the SIP process unexpectedly restarts. Cisco Bug IDs: CSCvc62590.
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Analysis
by VulDB Data Team • 01/25/2021
The vulnerability described in CVE-2017-12328 represents a critical denial of service weakness within Cisco IP Phone 8800 Series devices that operates at the Session Initiation Protocol (SIP) layer. This flaw specifically targets the SIP call handling mechanism, creating a condition where an unauthenticated remote attacker can trigger a system restart of the SIP process without requiring any credentials or prior access to the network. The vulnerability stems from inadequate validation of SIP packet headers, which fails to properly sanitize or verify incoming SIP communication data. The impact of this weakness extends beyond simple service disruption as it affects the fundamental communication capabilities of the device, causing all active phone calls to be terminated abruptly when the SIP process restarts. This creates significant operational disruption for users who rely on continuous communication services, particularly in enterprise environments where phone systems are critical infrastructure components.
The technical exploitation of this vulnerability follows a straightforward but effective attack pattern where an attacker crafts and sends a malformed SIP packet to the targeted Cisco IP Phone 8800 Series device. The incomplete input validation mechanism fails to properly process or reject these malformed packets, allowing them to be processed by the SIP handling component. When the SIP process encounters these invalid headers, it triggers an unexpected restart condition that propagates through the device's operating system. This restart process is not gracefully handled, resulting in immediate termination of all active calls and disruption of service. The vulnerability's classification aligns with CWE-20, which describes improper input validation as a fundamental weakness that allows malicious inputs to cause unintended behavior in applications. The specific nature of this flaw demonstrates how network protocols that handle real-time communication require robust validation mechanisms to prevent exploitation through crafted packet structures that can trigger system-level failures.
From an operational perspective, the impact of CVE-2017-12328 extends far beyond simple service interruption, creating cascading effects that can severely impact business continuity and communication infrastructure. The abrupt termination of all active calls during the SIP process restart creates immediate disruption for users, particularly in mission-critical environments where communication reliability is paramount. This vulnerability essentially provides an attacker with a means to perform remote service disruption without requiring authentication, making it particularly dangerous in environments where network security controls may not adequately protect telephony systems. The attack vector is particularly concerning because it operates over standard network protocols and does not require specialized tools or deep technical knowledge to execute, making it accessible to a broad range of threat actors. Organizations that deploy Cisco IP Phone 8800 Series devices face significant risk of service degradation or complete communication outages when this vulnerability is exploited, potentially affecting emergency services, customer support operations, and internal communications.
The mitigation strategies for this vulnerability primarily focus on implementing network-level protections and applying vendor-provided security updates. Cisco has released patches and software updates to address this specific vulnerability, which should be deployed immediately across all affected devices to prevent exploitation. Network administrators should implement access control measures such as firewalls and network segmentation to limit exposure of SIP-enabled devices to untrusted networks, reducing the attack surface available to potential attackers. Additionally, implementing monitoring systems that can detect unusual SIP traffic patterns or malformed packets may help identify exploitation attempts before they cause service disruption. The vulnerability's characteristics align with ATT&CK technique T1499.004, which describes network disruption attacks that specifically target communication systems. Organizations should also consider implementing redundant communication systems and backup procedures to maintain business continuity in case of successful exploitation. Regular security assessments and vulnerability scanning should be conducted to identify similar weaknesses in other network components and ensure comprehensive protection against similar threats. The remediation process requires careful coordination to minimize service disruption during patch deployment, particularly in large enterprise environments where multiple IP phones may be deployed across various locations.