CVE-2017-9478: Cisco DPC3939 Firmware

High severity, CVSS 7.5. EPSS: 1.5% chance of exploitation in the next 30 days.

The Comcast firmware on Cisco DPC3939 (firmware version dpc3939-P20-18-v303r20421733-160420a-CMCST) and DPC3939 (firmware version dpc3939-P20-18-v303r20421746-170221a-CMCST) devices sets the CM MAC address to a value with a two-byte offset from the MTA/VoIP MAC address, which indirectly allows remote attackers to discover hidden Home Security Wi-Fi networks by leveraging the embedding of the MTA/VoIP MAC address into the DNS hostname.

Affected products

• Cisco DPC3939 Firmware: version dpc3939-p20-18-v303r20421746-170221a-cmcst only; version dpc3939-p20-18-v303r20421733-160420a-cmcst only

Published 2017-07-31. Last modified 2026-06-17.