CVE-2026-7674 Overview
CVE-2026-7674 is a buffer overflow vulnerability in the Shenzhen Libituo Technology LBT-T300-HW1 router through firmware version 1.2.8. The flaw exists in the start_single_service function within the Web Management Interface. Attackers can trigger the overflow by manipulating the vpn_pptp_server or vpn_l2tp_server arguments. The vulnerability is exploitable remotely over the network and requires only low privileges. The vendor was contacted prior to public disclosure but did not respond, leaving affected devices without a coordinated patch.
Critical Impact
Remote attackers with low-privileged web access can corrupt memory in the router's management service, potentially leading to arbitrary code execution and full device compromise.
Affected Products
- Shenzhen Libituo Technology LBT-T300-HW1 firmware up to and including version 1.2.8
- Web Management Interface component containing the start_single_service function
- Devices exposing the vpn_pptp_server and vpn_l2tp_server configuration parameters
Discovery Timeline
- 2026-05-03 - CVE-2026-7674 published to NVD
- 2026-05-04 - Last updated in NVD database
Technical Details for CVE-2026-7674
Vulnerability Analysis
The vulnerability is classified under [CWE-119] as an improper restriction of operations within the bounds of a memory buffer. The flaw resides in the start_single_service function exposed through the LBT-T300-HW1 Web Management Interface. When a user supplies values for the vpn_pptp_server or vpn_l2tp_server parameters, the function copies the input into a fixed-size buffer without enforcing length validation. An authenticated attacker can submit an oversized payload through the management interface to overwrite adjacent memory. Successful exploitation undermines confidentiality, integrity, and availability of the router operating system.
Root Cause
The root cause is the absence of bounds checking on attacker-controlled VPN configuration arguments before they are passed to a stack or heap buffer inside start_single_service. The function trusts data originating from the web interface and writes it into memory without validating size or terminating bytes. This is a classic memory safety failure common in embedded router firmware written in C.
Attack Vector
The attack vector is network-based and requires low-privilege authentication to the Web Management Interface. An attacker with access to the management portal sends a crafted HTTP request setting vpn_pptp_server or vpn_l2tp_server to an oversized value. The malformed input triggers the overflow inside start_single_service, corrupting process memory. Depending on memory layout and protections, this may crash the service or allow control of execution flow on the device.
No verified exploit code is publicly available. The vulnerability mechanics are documented in the GitHub VPN Server Documentation and the VulDB Vulnerability #360827 entry.
Detection Methods for CVE-2026-7674
Indicators of Compromise
- Unexpected restarts or crashes of VPN-related services on the LBT-T300-HW1 router
- HTTP POST requests to the Web Management Interface containing unusually long vpn_pptp_server or vpn_l2tp_server parameter values
- Authenticated sessions originating from untrusted IP ranges modifying VPN server configuration
- New or unexpected outbound connections initiated by the router after configuration changes
Detection Strategies
- Inspect HTTP request bodies sent to the router management interface for parameter values exceeding expected lengths for VPN server fields
- Monitor router syslog and crash logs for repeated faults in the start_single_service process
- Apply network intrusion detection signatures matching oversized vpn_pptp_server or vpn_l2tp_server form parameters
- Compare current firmware version against 1.2.8 and flag any device at or below that level as exposed
Monitoring Recommendations
- Restrict management interface access to a dedicated administrative VLAN and log every authentication attempt
- Capture and retain HTTP request metadata to the router for retrospective analysis of parameter abuse
- Alert on configuration changes to PPTP and L2TP VPN settings outside of approved change windows
- Track outbound traffic from router management IPs to detect post-exploitation command-and-control activity
How to Mitigate CVE-2026-7674
Immediate Actions Required
- Remove the LBT-T300-HW1 Web Management Interface from any internet-facing network and restrict it to trusted internal hosts
- Rotate all administrative credentials used to access the router and disable any shared or default accounts
- Disable the PPTP and L2TP VPN server features if they are not required for business operations
- Place vulnerable devices behind a network segmentation boundary that filters HTTP traffic to the management port
Patch Information
No vendor patch is available. According to the disclosure, Shenzhen Libituo Technology was contacted before publication but did not respond. Organizations operating LBT-T300-HW1 hardware should treat the device as unpatched and consider replacement with a supported router platform. Monitor the VulDB Vulnerability #360827 entry for any future vendor response.
Workarounds
- Block external access to the router web management port using upstream firewall rules
- Require VPN or jump-host access for any administrative session targeting the router
- Disable vpn_pptp_server and vpn_l2tp_server configuration paths in the management interface where feasible
- Replace end-of-life or unsupported LBT-T300-HW1 units with vendor-supported equipment that receives security updates
# Example upstream firewall restriction for the router management interface
# Replace 10.0.0.0/24 with your administrative subnet and 192.0.2.10 with the router IP
iptables -A FORWARD -s 10.0.0.0/24 -d 192.0.2.10 -p tcp --dport 80 -j ACCEPT
iptables -A FORWARD -d 192.0.2.10 -p tcp --dport 80 -j DROP
iptables -A FORWARD -d 192.0.2.10 -p tcp --dport 443 -j DROP
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
