Bastille Tracking Number 30 CVE-2017-9487 Overview The wan0 IPv6 address on certain gateways has been observed to be generated from the gateway's CM MAC. With knowledge of the CM MAC (Bastille Tracking Numbers 19, 20, 27), an attacker is able generate the target wan0 IPv6 address. Affected Platforms Cisco DPC3939, firmware version dpc3939-P20-18-v303r20421746-170221a-CMCST Cisco DPC3941T, firmware version DPC3941_2.5s3_PROD_sey Proof-of-Concept The wan0 IPv6 address is generated based on the CM MAC of a given gateway and a region identifier. Given the following inputs: Region identifier: 40:11 (Atlanta) Unknown octet: 53 (Unknown how this is defined, but can be brute-forced) MAC address: 11:22:33:44:55:66 The following IPv6 address is generated: 2001:0558:4011:0053:1122:33FF:FE44:5566 Test Environment Cisco DPC3939, firmware version dpc3939-P20-18-v303r20421746-170221a-CMCST Cisco DPC3941T, firmware version DPC3941_2.5s3_PROD_sey Mitigation There is no apparent mechanism to allow Comcast customers to control or change this behavior. Recommended Remediation Move to certificate-based authentication. Credits Marc Newlin and Logan Lamb, Bastille Chris Grayson, Web Sight.IO