CVE-2021-25436
📋 TL;DR
CVE-2021-25436 is an improper input validation vulnerability in Tizen's FOTA (Firmware Over-The-Air) service that allows arbitrary code execution via the Samsung Accessory Protocol. Attackers can exploit this to execute malicious code with system privileges on affected devices. This affects Tizen-based Samsung devices including smartwatches, TVs, and other IoT products.
💻 Affected Systems
- Samsung smartwatches (Tizen-based)
- Samsung smart TVs (Tizen-based)
- Other Tizen IoT devices
📦 What is this software?
Tizen by Linux
⚠️ Risk & Real-World Impact
Worst Case
Complete device compromise allowing attacker to install persistent malware, steal sensitive data, brick devices, or use devices as part of botnets.
Likely Case
Remote code execution leading to data theft, surveillance capabilities, or device manipulation.
If Mitigated
Limited impact if devices are patched and network access is restricted to trusted accessories only.
🎯 Exploit Status
Exploitation requires network access to the device's accessory protocol interface.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Firmware update JUL-2021 Release or later
Vendor Advisory: https://security.samsungmobile.com/serviceWeb.smsb?year=2021&month=7
Restart Required: Yes
Instructions:
1. Check for firmware updates in device settings. 2. Install July 2021 or later firmware update. 3. Restart device after installation.
🔧 Temporary Workarounds
Disable Bluetooth/accessory connections
allTemporarily disable Bluetooth and accessory connections to prevent exploitation via Samsung Accessory Protocol
Network segmentation
allIsolate Tizen devices on separate network segments to limit attack surface
🧯 If You Can't Patch
- Disable FOTA service if not required for device functionality
- Implement strict network access controls to limit which devices can communicate with Tizen devices
🔍 How to Verify
Check if Vulnerable:
Check firmware version in device settings. If version is prior to July 2021 update, device is vulnerable.Check Version:
Device-specific: Check Settings > About Device > Software Information on Tizen devicesVerify Fix Applied:
Verify firmware version shows July 2021 or later update installed in device settings.📡 Detection & Monitoring
Log Indicators:
- Unusual accessory protocol connections
- FOTA service errors or crashes
- Unexpected firmware update attempts
Network Indicators:
- Unusual Bluetooth or accessory protocol traffic to Tizen devices
- Suspicious network connections to FOTA service ports
SIEM Query:
device_type:Tizen AND (event_type:accessory_connection OR event_type:fota_update) AND status:failed OR status:unusual