CVE-2023-25086
📋 TL;DR
This vulnerability allows authenticated attackers with high privileges to execute arbitrary code on Milesight UR32L routers by sending specially crafted HTTP requests that trigger buffer overflows in the vtysh_ubus binary. The vulnerability affects Milesight UR32L routers running vulnerable firmware versions due to unsafe sprintf usage in firewall_handler_set function.
💻 Affected Systems
- Milesight UR32L
📦 What is this software?
Ur32l Firmware by Milesight
⚠️ Risk & Real-World Impact
Worst Case
Complete system compromise with root-level arbitrary code execution, allowing attackers to install persistent backdoors, pivot to internal networks, or disrupt network operations.
Likely Case
Privileged authenticated attackers gaining remote code execution to modify router configurations, intercept traffic, or use the device as a foothold for lateral movement.
If Mitigated
Limited impact if proper network segmentation, least privilege access controls, and monitoring are implemented to detect suspicious HTTP requests.
🎯 Exploit Status
Exploitation requires authenticated access with high privileges and crafting specific HTTP requests to trigger the buffer overflow.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Not specified in available references
Vendor Advisory: Not found in provided references
Restart Required: Yes
Instructions:
1. Check Milesight security advisories for firmware updates. 2. Download and verify the latest firmware. 3. Backup current configuration. 4. Apply firmware update via web interface or CLI. 5. Reboot device. 6. Verify update was successful.
🔧 Temporary Workarounds
Restrict HTTP Access
linuxLimit HTTP access to the router's management interface to trusted networks only.
iptables -A INPUT -p tcp --dport 80 -s TRUSTED_NETWORK -j ACCEPT
iptables -A INPUT -p tcp --dport 80 -j DROP
Disable Unnecessary Services
linuxDisable HTTP management interface if not required, using alternative management methods.
systemctl stop httpd
systemctl disable httpd
🧯 If You Can't Patch
- Implement strict network segmentation to isolate UR32L routers from critical networks.
- Enforce least privilege access controls and monitor for suspicious HTTP requests to the management interface.
🔍 How to Verify
Check if Vulnerable:
Check firmware version via web interface or CLI command: 'cat /etc/version' or similar. If version is v32.3.0.5 or potentially earlier, device is vulnerable.Check Version:
cat /etc/versionVerify Fix Applied:
After updating firmware, verify version is newer than v32.3.0.5 using same version check command.📡 Detection & Monitoring
Log Indicators:
- Unusual HTTP POST requests to firewall-related endpoints
- Multiple failed authentication attempts followed by successful login and HTTP requests
- Process crashes or abnormal behavior in vtysh_ubus binary
Network Indicators:
- HTTP traffic to router management interface containing unusually long parameter values for index or dport
- Traffic patterns suggesting buffer overflow attempts
SIEM Query:
source="router_logs" AND (http_method="POST" AND uri CONTAINS "firewall" AND (param_length>100 OR contains(buffer_overflow_patterns)))