CVE-2018-0197 in IOS
Summary
by MITRE
A vulnerability in the VLAN Trunking Protocol (VTP) subsystem of Cisco IOS Software and Cisco IOS XE Software could allow an unauthenticated, adjacent attacker to corrupt the internal VTP database on an affected device and cause a denial of service (DoS) condition. The vulnerability is due to a logic error in how the affected software handles a subset of VTP packets. An attacker could exploit this vulnerability by sending VTP packets in a sequence that triggers a timeout in the VTP message processing code of the affected software. A successful exploit could allow the attacker to impact the ability to create, modify, or delete VLANs and cause a DoS condition. There are workarounds that address this vulnerability. This vulnerability affects Cisco devices that are running a vulnerable release of Cisco IOS Software or Cisco IOS XE Software, are operating in VTP client mode or VTP server mode, and do not have a VTP domain name configured. The default configuration for Cisco devices that are running Cisco IOS Software or Cisco IOS XE Software and support VTP is to operate in VTP server mode with no domain name configured.
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Analysis
by VulDB Data Team • 10/30/2025
The vulnerability identified as CVE-2018-0197 resides within the VLAN Trunking Protocol subsystem of Cisco IOS and IOS XE software implementations, representing a critical security flaw that undermines network infrastructure integrity. This vulnerability specifically targets devices configured in VTP client or server modes without a configured VTP domain name, creating an exploitable condition that affects the fundamental operation of VLAN management within Cisco network environments. The flaw manifests as a logic error in the processing of VTP packets, where certain sequences of packets can trigger unexpected behavior in the VTP message handling code, leading to potential system instability and service disruption.
The technical exploitation of this vulnerability requires an adjacent attacker who can send crafted VTP packets to the target device, leveraging a specific sequence that causes a timeout condition within the VTP message processing code. This timeout occurs due to improper handling of certain packet structures that should be processed gracefully but instead trigger an internal state corruption within the VTP database. The vulnerability operates at the network protocol level, specifically within the VTP implementation that governs how VLAN information is distributed across network switches. This weakness directly impacts the availability and functionality of VLAN management operations, as the corrupted internal database prevents normal VLAN creation, modification, or deletion activities from functioning properly.
The operational impact of CVE-2018-0197 extends beyond simple denial of service to potentially compromise network segmentation and security policies that rely on proper VLAN configuration. When exploited successfully, the vulnerability can cause complete disruption of VLAN services, forcing network administrators to implement emergency maintenance procedures and potentially affecting business continuity. The default configuration of Cisco devices operating in VTP server mode without domain name configuration creates a widespread exposure surface, as the vulnerability affects the majority of devices in their standard operational state. This makes the vulnerability particularly dangerous in enterprise environments where network stability and availability are paramount to business operations.
Network security professionals should consider this vulnerability in relation to CWE-129, which addresses improper handling of input boundaries, and CWE-362, which covers concurrent execution using shared resource access. The attack pattern aligns with ATT&CK technique T1499.004, which involves network disruption through manipulation of network protocols and services. The vulnerability's design flaw in VTP packet processing creates a condition where malformed or specially crafted packets can cause timeout conditions, leading to resource exhaustion and service unavailability. Organizations should implement mitigations including disabling VTP when not required, configuring strong VTP domain passwords, and ensuring proper network segmentation to limit the attack surface. The recommended workaround involves configuring a VTP domain name, which prevents the vulnerable code path from being executed, thereby protecting against this specific exploitation vector while maintaining network functionality.