Cisco IOS/IOS XE VLAN Trunking Protocol input validation

Summaryinfo

A vulnerability identified as problematic has been detected in Cisco IOS and IOS XE. This affects an unknown part of the component VLAN Trunking Protocol. This manipulation causes input validation. The identification of this vulnerability is CVE-2018-0197. The attack needs to be done within the local network. There is no exploit available. You should upgrade the affected component.

Detailsinfo

A vulnerability was found in Cisco IOS and IOS XE (Router Operating System) (affected version not known). It has been declared as problematic. Affected by this vulnerability is some unknown functionality of the component VLAN Trunking Protocol. The manipulation with an unknown input leads to a input validation vulnerability. The CWE definition for the vulnerability is CWE-20. The product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly. As an impact it is known to affect availability. The summary by CVE is:

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.

The bug was discovered 09/26/2018. The weakness was shared 10/05/2018 as cisco-sa-20180926-vtp as confirmed advisory (Website). It is possible to read the advisory at tools.cisco.com. This vulnerability is known as CVE-2018-0197 since 11/26/2017. The attack can only be initiated within the local network. The exploitation doesn't need any form of authentication. The technical details are unknown and an exploit is not publicly available. The advisory points out:

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.

The vulnerability was handled as a non-public zero-day exploit for at least 9 days. During that time the estimated underground price was around $5k-$25k. The commercial vulnerability scanner Qualys is able to test this issue with plugin 316350 (Cisco IOS and IOS XE Software VLAN Trunking Protocol Denial of Service Vulnerability(cisco-sa-20180926-vtp)).

Upgrading eliminates this vulnerability. The advisory contains the following remark:

To prevent exploitation of this vulnerability, administrators can configure a VTP domain name for a device by using the vtp domain configuration command in the CLI.

The vulnerability is also documented in the vulnerability database at SecurityFocus (BID 105424†). Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.

Productinfo

Type

• Router Operating System

Vendor

• Cisco

Name

• IOS
• IOS XE

License

• commercial

Website

• Vendor: https://www.cisco.com/

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