CVE-2021-27954
📋 TL;DR
A heap-based buffer overflow vulnerability in the HomeKit setup process of ecobee3 lite smart thermostats allows attackers to force devices to connect to malicious SSIDs or crash the device. This affects ecobee3 lite devices running firmware version 4.5.81.200. Attackers within wireless range can exploit this without authentication.
💻 Affected Systems
- ecobee3 lite smart thermostat
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Attacker gains control of thermostat, manipulates temperature settings, uses device as pivot point for network attacks, or bricks the device permanently.
Likely Case
Attacker forces device to connect to rogue access point for man-in-the-middle attacks, or causes temporary denial of service requiring physical reset.
If Mitigated
Device remains functional but may require occasional resets if targeted by denial of service attacks.
🎯 Exploit Status
Exploit requires attacker to be within wireless range during device setup/configuration.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 4.6.33.73 or later
Vendor Advisory: https://support.ecobee.com/s/articles/ecobee-Security-Advisory
Restart Required: Yes
Instructions:
1. Open ecobee mobile app 2. Navigate to Settings > About > Version 3. Check if update is available 4. Install firmware update 5. Device will restart automatically
🔧 Temporary Workarounds
Disable HomeKit Wireless Access Control
allPrevent exploitation by disabling the vulnerable feature during setup
Physical isolation during setup
allPerform initial device setup in physically secure location away from potential attackers
🧯 If You Can't Patch
- Physically isolate device from untrusted wireless networks
- Monitor for unexpected device behavior or connection to unknown SSIDs
🔍 How to Verify
Check if Vulnerable:
Check firmware version in ecobee app: Settings > About > Version. If version is 4.5.81.200, device is vulnerable.Check Version:
Not applicable - use ecobee mobile app interfaceVerify Fix Applied:
Confirm firmware version is 4.6.33.73 or later in ecobee app settings.📡 Detection & Monitoring
Log Indicators:
- Unexpected device resets
- Connection to unknown SSIDs
- Failed HomeKit pairing attempts
Network Indicators:
- Device connecting to unexpected wireless networks
- Unusual network traffic from thermostat
SIEM Query:
Not applicable - device logs not typically integrated into SIEM