Power users often ask: Can I install open-source firmware like OpenWrt or DD-WRT on the Fast 5670?
Short answer: Extremely difficult and not recommended for most users.
Long answer: The Sagemcom Fast 5670 uses a Broadcom chipset with proprietary drivers for DOCSIS. The cable modem portion is locked down by your ISP. Replacing the firmware would break DOCSIS binding, meaning you lose internet completely. Additionally: Sagemcom Fast 5670 Firmware
If you want advanced features (VPN server, ad-blocking, custom QoS), consider placing the Fast 5670 in bridge mode and connecting your own third-party router (e.g., Asus or Raspberry Pi running OpenWrt). This leaves the cable modem firmware untouched while giving you control over the routing firmware.
Many ISPs now offer companion apps. Within the app, go to: Power users often ask: Can I install open-source
Firmware version numbers for the Fast 5670 (e.g., SG5670_1.1.5.0 or FAST_5670_2.3.2) are critical indicators of security posture. Historically, several CVEs have affected Broadcom-based chipsets used in this device, including:
Because ISPs control firmware updates, users are at the mercy of their provider’s patch cadence. Some ISPs push updates automatically in the background (invisible to the user); others require manual checks. Worse, many users never receive updates after 2–3 years, leaving the gateway exposed. The firmware lacks modern features like automatic HTTPS for the admin panel (defaulting to HTTP) or certificate pinning, making local network sniffing a risk. If you want advanced features (VPN server, ad-blocking,
A niche but frustrating issue: Some ISPs automatically "roll back" your firmware to an older version if they detect a manual update that bypasses their testing. If you manually updated to a newer Sagemcom Fast 5670 Firmware to fix a specific bug, and your ISP keeps reverting it: