CVE-2026-3556: Philips Hue Bridge V2 Firmware RCE Flaw

CVE-2026-3556 Overview

CVE-2026-3556 is a heap-based buffer overflow vulnerability in the Philips Hue Bridge V2 affecting the HomeKit pair-setup process. The flaw resides in the hk_hap_pair_storage_put function, which copies user-supplied data into a fixed-length heap buffer without validating the input length. Network-adjacent attackers can exploit this issue without authentication to execute arbitrary code in the context of the HomeKit service. The vulnerability is classified under [CWE-122] Heap-based Buffer Overflow and was reported through the Zero Day Initiative as ZDI-CAN-28326.

Critical Impact
Unauthenticated adjacent-network attackers can achieve remote code execution on Philips Hue Bridge V2 devices through the HomeKit service, compromising connected smart home environments.

Affected Products

Philips Hue Bridge V2
Philips Hue Bridge V2 Firmware (all versions prior to vendor patch)
Smart home deployments exposing HomeKit pair-setup on local networks

Discovery Timeline

2026-03-16 - CVE-2026-3556 published to NVD
2026-04-27 - Last updated in NVD database

Technical Details for CVE-2026-3556

Vulnerability Analysis

The vulnerability exists in the HomeKit Accessory Protocol (HAP) implementation on the Philips Hue Bridge V2. The hk_hap_pair_storage_put function handles persistence of pairing data during the HomeKit pair-setup exchange. Attackers can send a crafted pair-setup request containing oversized fields. The function copies that input into a fixed-size heap allocation without bounds checking. Adjacent buffer corruption can overwrite heap metadata and adjacent objects, leading to control of execution flow.

Successful exploitation yields code execution within the HomeKit service process running on the bridge. Because the bridge mediates control of every paired smart device on the network, an attacker can pivot to manipulate lighting, sensors, and integrated third-party accessories. The bridge can also be repurposed as a persistent foothold on the local network.

Root Cause

The root cause is the absence of length validation prior to a memory copy operation in hk_hap_pair_storage_put. The function trusts attacker-controlled length values from the pair-setup payload and writes beyond the bounds of a fixed-length heap buffer, corrupting adjacent heap structures.

Attack Vector

Exploitation requires adjacent network access, meaning the attacker must reside on the same logical network segment as the bridge, such as the local Wi-Fi or wired LAN. No authentication is required because the vulnerable code path is reachable during the initial HomeKit pair-setup handshake. An attacker associated with the network, including through a compromised IoT device or guest Wi-Fi, can deliver the malicious payload directly to the bridge.

The vulnerability is described in detail in the Zero Day Initiative Advisory ZDI-26-154. No public proof-of-concept exploit is currently available.

Detection Methods for CVE-2026-3556

Indicators of Compromise

Unexpected HomeKit pair-setup requests originating from unknown devices on the local network
Philips Hue Bridge V2 process crashes, restarts, or watchdog resets coinciding with HAP traffic
Unusual outbound connections from the Hue Bridge to unfamiliar IP addresses following pair-setup attempts
Anomalous control commands issued to paired accessories without corresponding user activity

Detection Strategies

Monitor local network traffic on TCP port 80 and the mDNS-advertised HAP ports for malformed pair-setup messages
Inspect HomeKit TLV (Type-Length-Value) payloads for oversized fields that exceed protocol expectations
Baseline expected pairing activity and alert on repeated pair-setup attempts from a single source
Correlate bridge restart events with preceding network sessions to identify exploitation attempts

Monitoring Recommendations

Place IoT devices on a segmented VLAN and log all traffic destined to the Hue Bridge
Enable wireless intrusion detection to flag rogue devices joining the network segment hosting the bridge
Forward bridge syslog and Apple Home hub event data to a centralized SIEM for correlation
Review router DHCP and ARP tables regularly for unauthorized clients on the IoT segment

How to Mitigate CVE-2026-3556

Immediate Actions Required

Apply the latest Philips Hue Bridge V2 firmware update as soon as it becomes available through the Hue mobile application
Isolate the Hue Bridge on a dedicated IoT VLAN with no inbound access from guest or untrusted networks
Restrict Wi-Fi access using WPA3 or WPA2 with strong credentials to limit adjacent-network exposure
Disable HomeKit integration on bridges that do not require it until a patch is installed

Patch Information

Philips has been notified through the Zero Day Initiative coordinated disclosure process. Administrators should monitor the Zero Day Initiative Advisory ZDI-26-154 and the official Philips Hue support channels for firmware availability. The Hue mobile application automatically delivers firmware updates when the bridge is connected to the internet and update notifications are enabled.

Workarounds

Block adjacent-network access to the bridge by enforcing strict VLAN segmentation and firewall ACLs
Disable automatic HomeKit pairing advertisement when not actively onboarding new accessories
Remove untrusted devices from the local network and audit existing wireless clients
Power off the bridge when extended remote management is not required in high-risk environments

bash

# Example firewall rule isolating the Hue Bridge on an IoT VLAN
# Replace 10.20.0.10 with the bridge IP and 10.20.0.0/24 with the IoT subnet
iptables -A FORWARD -s 10.0.0.0/24 -d 10.20.0.10 -j DROP
iptables -A FORWARD -s 10.20.0.10 -d 10.0.0.0/24 -j DROP
iptables -A FORWARD -i wlan-guest -d 10.20.0.0/24 -j DROP