CVE-2025-7837
📋 TL;DR
A critical buffer overflow vulnerability exists in the MQTT service of TOTOLINK T6 routers, specifically in the recvSlaveStaInfo function. Attackers can remotely exploit this by manipulating the 'dest' argument to execute arbitrary code or crash the device. This affects TOTOLINK T6 routers running firmware version 4.1.5cu.748_B20211015.
💻 Affected Systems
- TOTOLINK T6 router
📦 What is this software?
T6 Firmware by Totolink
⚠️ Risk & Real-World Impact
Worst Case
Remote code execution leading to complete device compromise, persistence, lateral movement, and data exfiltration.
Likely Case
Device crash causing denial of service, potentially requiring physical reset or firmware reflash.
If Mitigated
Limited impact if network segmentation prevents access to vulnerable service.
🎯 Exploit Status
Proof-of-concept exploit code is publicly available on GitHub, making exploitation straightforward for attackers.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Unknown
Vendor Advisory: None known
Restart Required: Yes
Instructions:
No official patch available. Check TOTOLINK website for firmware updates. If update exists: 1. Download firmware from vendor site. 2. Access router admin interface. 3. Navigate to firmware update section. 4. Upload and apply new firmware. 5. Reboot router.
🔧 Temporary Workarounds
Disable MQTT Service
allTurn off the vulnerable MQTT service if not required for functionality.
Check router admin interface for MQTT/IoT service settings and disable
Network Segmentation
allIsolate TOTOLINK T6 routers from critical networks and internet exposure.
Configure firewall rules to block external access to router MQTT port (typically 1883/tcp)
🧯 If You Can't Patch
- Replace affected routers with different models or brands that are not vulnerable
- Implement strict network access controls to limit exposure to only trusted management networks
🔍 How to Verify
Check if Vulnerable:
Check router firmware version in admin web interface. If version is exactly 4.1.5cu.748_B20211015, device is vulnerable.Check Version:
Login to router admin interface and check System Status or Firmware Information pageVerify Fix Applied:
After applying any firmware update, verify version has changed from 4.1.5cu.748_B20211015.📡 Detection & Monitoring
Log Indicators:
- Unusual MQTT connection attempts
- Router crash/reboot logs
- Buffer overflow error messages in system logs
Network Indicators:
- Unexpected traffic to router MQTT port (1883/tcp)
- Malformed MQTT packets targeting the recvSlaveStaInfo function
SIEM Query:
source="router_logs" AND ("MQTT" OR "buffer overflow" OR "recvSlaveStaInfo")