CVE-2017-12318 in RF Gateway 1
Summary
by MITRE
A vulnerability in the TCP state machine of Cisco RF Gateway 1 devices could allow an unauthenticated, remote attacker to prevent an affected device from delivering switched digital video (SDV) or video on demand (VoD) streams, resulting in a denial of service (DoS) condition. The vulnerability is due to a processing error with TCP connections to the affected device. An attacker could exploit this vulnerability by establishing a large number of TCP connections to an affected device and not actively closing those TCP connections. A successful exploit could allow the attacker to prevent the affected device from delivering SDV or VoD streams to set-top boxes. Cisco Bug IDs: CSCvf19887.
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Analysis
by VulDB Data Team • 12/07/2019
The vulnerability identified as CVE-2017-12318 resides within the TCP state machine implementation of Cisco RF Gateway 1 devices, representing a critical denial of service weakness that undermines the device's ability to deliver essential video services. This flaw specifically targets the handling of TCP connections, creating a scenario where an attacker can manipulate the device's connection management processes to disrupt legitimate service delivery. The affected Cisco RF Gateway 1 devices operate in environments where continuous video streaming is critical for user experience, making this vulnerability particularly dangerous as it directly impacts the core functionality of the device's video delivery capabilities.
The technical exploitation of this vulnerability stems from a processing error within the TCP state machine that governs how the device manages incoming connection requests and maintains active connection states. When an attacker establishes a large volume of TCP connections to the device without properly closing them, the system's TCP connection handling mechanism becomes overwhelmed and enters a degraded state. This condition prevents the device from properly managing its resources and maintaining the necessary connections for delivering switched digital video and video on demand streams to connected set-top boxes. The flaw essentially creates a resource exhaustion scenario where legitimate TCP connection requests cannot be processed due to the device's inability to manage the excessive number of half-open or inactive connections.
The operational impact of this vulnerability extends beyond simple service disruption, as it fundamentally compromises the availability of video services that users depend upon. Set-top boxes connected to the affected Cisco RF Gateway 1 devices would experience complete or partial loss of SDV and VoD streaming capabilities, potentially affecting thousands of users simultaneously depending on the scale of the attack. The vulnerability's remote and unauthenticated nature means that attackers can exploit it from anywhere on the network without requiring any credentials or privileged access, making it particularly dangerous for network administrators who must defend against such attacks. This characteristic aligns with ATT&CK technique T1499.004 for network denial of service attacks and represents a classic case of resource exhaustion as outlined in CWE-400.
Mitigation strategies for this vulnerability should focus on implementing TCP connection rate limiting and connection tracking mechanisms to prevent the exploitation of the TCP state machine flaw. Network administrators should configure the affected devices with appropriate connection limits and implement connection timeouts to automatically terminate inactive connections. Additionally, deploying network access control lists and implementing TCP stack hardening measures can help reduce the attack surface. The vulnerability's nature suggests that implementing proper TCP connection management policies and monitoring for unusual connection patterns would provide effective protection against exploitation attempts. Cisco recommends applying the latest software patches and firmware updates to address the underlying TCP state machine implementation issues that contribute to this vulnerability, while also implementing network segmentation to limit the potential impact of successful exploitation attempts.