FortiGate 80F SFP Bypass Relay Stuck in Closed State on Power Loss
On FortiGate 80F and 81F Bypass models, mechanical optical and copper bypass relays fail to disengage after cold power restoration, leaving traffic physically bridged across ports and completely bypassing firewall security inspection.
Technical Root Cause Analysis
The FortiGate 80F/81F Bypass hardware platform includes physical telecom latching relays managed by an auxiliary CPLD micro-controller and a low-level Broadcom Linux kernel driver (relay_drv / bcm_bypass.ko). When power to the firewall drops, the de-energized relay contacts close, directly bridging port1 to port2 (or SFP bypass cages) to preserve line-rate Layer 1/2 physical continuity for in-line industrial or telecom backbones.
Under Bug 0862419, following a cold boot or utility power return, the kernel driver issues the GPIO unlatch pulse before the onboard switching bus and SFP PHY controllers complete their power-on sequence. Because the pulse width (nominal 80ms) is too short and issued while the CPLD voltage rail is still stabilizing, the mechanical solenoid fails to overcome magnetic hysteresis. The relay remains stuck in the bypass position while FortiOS boots completely, rendering all firewall policies, NAT, and UTM engines ineffective as wire packets bypass the CPU and SOC4 ASIC entirely.
Affected Firmware & Blast Radius Matrix
| FortiOS Branch | Vulnerable Builds | Confirmed Clean Build | Status & Workaround |
|---|---|---|---|
| FortiOS 7.2 | 7.2.2 – 7.2.5 | 7.2.6+ | Manual CLI unlatch command via fnsysctl |
| FortiOS 7.0 | 7.0.8 – 7.0.13 | 7.0.14+ | Apply watchdog auto-bypass delay |
| FortiOS 7.4 | Not Affected | 7.4.0+ | CPLD driver initialization delay incorporated |
Platform Impact: Exclusively affects FortiGate 80F-Bypass and FortiGate 81F-Bypass appliances deployed in inline fail-open/fail-closed industrial and branch topologies.
Step 01: Free Verification CLI (Safe Read-Only)
Execute these diagnostic commands to query the physical bypass state and detect any discrepancy between the FortiOS data plane and the CPLD hardware relay:
Diagnostic Commands
# 1. Inspect physical hardware bypass controller status
diagnose hardware deviceinfo bypass
# 2. Query the low-level Broadcom bypass driver registers directly
fnsysctl cat /proc/net/bcm/bypass
# 3. Test relay responsiveness and view current latching state
diagnose hardware test bypassRemediation & Workaround Steps (Teaser Preview)
Follow the complete step-by-step remediation guide in the Ferrite interactive platform:
Frequently Asked Questions
Check diagnose hardware deviceinfo bypass. If the status reports BYPASS while the firewall is fully powered on and responsive via management, traffic is bypassing inspection.
Yes. You can issue low-level driver commands via SSH or FortiManager CLI script to pulse the CPLD unlatch register, snapping the mechanical relay back into normal inline operation.
No. Only specific hardware SKUs designated as FortiGate 80F-Bypass and FortiGate 81F-Bypass include mechanical telecom bypass relays.