CVE-2025-5671 Overview
CVE-2025-5671 is a buffer overflow vulnerability in the TOTOLINK N302R Plus router firmware through version 3.4.0-B20201028. The flaw resides in the HTTP POST request handler at /boafrm/formPortFw, where the service_type parameter is processed without sufficient bounds checking. Authenticated attackers can manipulate this argument over the network to overflow a fixed-size buffer. The exploit details have been published, increasing the risk of opportunistic attacks against exposed devices. The vulnerability is tracked as CWE-119: Improper Restriction of Operations within the Bounds of a Memory Buffer.
Critical Impact
Remote attackers with low-privilege credentials can trigger memory corruption in the router's web server, potentially leading to arbitrary code execution or device compromise.
Affected Products
- TOTOLINK N302R Plus router (hardware)
- TOTOLINK N302R Plus firmware versions up to and including 3.4.0-B20201028
- Deployments exposing the device web administration interface on internal or external networks
Discovery Timeline
- 2025-06-05 - CVE-2025-5671 published to NVD
- 2025-06-17 - Last updated in NVD database
Technical Details for CVE-2025-5671
Vulnerability Analysis
The vulnerability exists in the TOTOLINK N302R Plus embedded HTTP server (Boa-derived), which exposes the URL endpoint /boafrm/formPortFw for port forwarding configuration. When the handler parses POST parameters, the service_type field is copied into a fixed-size stack or heap buffer without validating the input length. Supplying an oversized value corrupts adjacent memory.
On MIPS-based embedded devices like the N302R Plus, such overflows commonly overwrite saved return addresses or function pointers. An attacker who controls overflow contents can redirect execution to attacker-supplied data, often using return-oriented programming (ROP) gadgets within the firmware. Successful exploitation grants code execution in the context of the web server process, which typically runs as root on consumer routers.
Root Cause
The root cause is missing length validation on the service_type POST parameter before it is copied into a destination buffer. The firmware relies on unsafe string-handling routines such as strcpy or sprintf without enforcing maximum input sizes, satisfying the conditions described in CWE-119.
Attack Vector
The attack is delivered over the network through a single crafted HTTP POST request to /boafrm/formPortFw. Exploitation requires low-privilege authentication to the web interface. Devices with default or weak credentials, or those exposed to the WAN, present the greatest risk. Refer to the public CVE documentation and VulDB entry 311160 for technical details on the request structure and overflowing field.
Detection Methods for CVE-2025-5671
Indicators of Compromise
- HTTP POST requests to /boafrm/formPortFw containing abnormally long service_type parameter values
- Unexpected reboots or crashes of the router web management daemon following inbound HTTP traffic
- Outbound connections from the router to unknown hosts, indicating possible post-exploitation command-and-control activity
- New or modified port-forwarding entries that were not configured by an administrator
Detection Strategies
- Inspect web access logs and network captures for POST requests to /boafrm/formPortFw where the service_type field exceeds expected lengths (typically a short service name)
- Deploy network intrusion detection signatures that flag oversized form fields targeting TOTOLINK URI patterns
- Monitor DNS and NetFlow telemetry from router IP addresses for anomalies consistent with router compromise
Monitoring Recommendations
- Forward router syslog and firewall logs to a centralized SIEM for correlation with network telemetry
- Baseline normal administrative access to the router web UI and alert on deviations in source IPs or request volumes
- Track firmware version inventory across deployed TOTOLINK devices to identify unpatched units
How to Mitigate CVE-2025-5671
Immediate Actions Required
- Block external access to the router web administration interface from the WAN and restrict management to a trusted internal segment
- Change default credentials on all TOTOLINK N302R Plus devices and enforce strong, unique passwords
- Disable the port forwarding configuration page or the embedded HTTP server entirely if not required
- Inspect existing port-forwarding rules for unauthorized entries and remove any that are not legitimate
Patch Information
No vendor-supplied patch has been published in the references at the time of NVD entry. Monitor the TOTOLINK security page for firmware updates addressing CVE-2025-5671. If no fix is available, consider replacing the device with a supported model that receives current security maintenance.
Workarounds
- Place the router behind an upstream firewall and restrict TCP access to the management ports (typically 80/443) to administrator workstations only
- Use network segmentation to prevent untrusted clients on the LAN from reaching the management interface
- Disable remote management features and UPnP to reduce the attack surface exposed by the embedded web server
# Example: Restrict access to the router web UI from a trusted host using iptables
iptables -A INPUT -p tcp --dport 80 -s 192.0.2.10 -j ACCEPT
iptables -A INPUT -p tcp --dport 80 -j DROP
iptables -A INPUT -p tcp --dport 443 -s 192.0.2.10 -j ACCEPT
iptables -A INPUT -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.
