CVE-2025-5672: Totolink N302r Plus Buffer Overflow Flaw

CVE-2025-5672 Overview

CVE-2025-5672 is a buffer overflow vulnerability affecting TOTOLINK N302R Plus routers up to firmware version 3.4.0-B20201028. The flaw resides in the /boafrm/formFilter endpoint handled by the HTTP POST request handler. Attackers can manipulate the url argument to trigger a buffer overflow condition [CWE-119]. The vulnerability is exploitable remotely over the network and the exploit details have been publicly disclosed. Successful exploitation can lead to memory corruption and potential code execution on the affected device.

Critical Impact
Remote attackers with low privileges can trigger memory corruption on TOTOLINK N302R Plus routers through the formFilter endpoint, potentially compromising the device and the network behind it.

Affected Products

TOTOLINK N302R Plus router hardware
TOTOLINK N302R Plus firmware up to 3.4.0-B20201028
Networks relying on the affected N302R Plus devices as edge equipment

Discovery Timeline

2025-06-05 - CVE-2025-5672 published to NVD
2026-06-17 - Last updated in NVD database

Technical Details for CVE-2025-5672

Vulnerability Analysis

The vulnerability exists in the HTTP POST request handler that processes requests to /boafrm/formFilter on the TOTOLINK N302R Plus router. The handler accepts user-supplied input through the url parameter and copies it into a fixed-size stack or heap buffer without enforcing proper bounds checks. This improper restriction of operations within memory buffer limits maps to [CWE-119]. Supplying an oversized url value overflows the destination buffer, overwriting adjacent memory regions. Depending on the layout of memory at the time of exploitation, this can corrupt control data such as saved return addresses or function pointers used by the boa web server process.

Root Cause

The root cause is missing input length validation in the firmware's request parsing logic for the formFilter endpoint. The boa-based web server in TOTOLINK devices passes attacker-controlled HTTP POST parameters directly into memory copy routines that assume bounded input. Because no length check or safe string handling routine is enforced, any POST body containing a long url value will overflow the receiving buffer.

Attack Vector

An attacker reaches the vulnerable endpoint by sending a crafted HTTP POST request to /boafrm/formFilter on the router's management interface. Exploitation requires network reachability to the device and authenticated access at a low privilege level. When the router's management interface is exposed to the WAN, the attack surface extends beyond the local network. Public disclosure of the vulnerability details increases the risk of opportunistic exploitation. No verified proof-of-concept code is reproduced here; refer to the GitHub CVE Documentation and VulDB entry #311161 for technical specifics.

Detection Methods for CVE-2025-5672

Indicators of Compromise

HTTP POST requests to /boafrm/formFilter containing abnormally long url parameter values
Unexpected reboots, crashes, or service interruptions of the boa web server on N302R Plus devices
Outbound connections from the router to unknown hosts following suspicious management interface traffic
New or modified firewall, routing, or DNS configuration entries that were not initiated by administrators

Detection Strategies

Inspect HTTP traffic destined for router management interfaces and flag POST bodies to /boafrm/formFilter exceeding expected parameter lengths
Correlate router log entries showing repeated formFilter requests with subsequent device instability or restarts
Monitor for management interface access originating from non-administrative source IP addresses, particularly from WAN-side sources

Monitoring Recommendations

Aggregate router syslog and HTTP access logs into a centralized analytics platform for retention and anomaly detection
Alert on any HTTP request to TOTOLINK administrative endpoints originating from outside defined management subnets
Track firmware versions across deployed N302R Plus units and flag devices still running 3.4.0-B20201028 or earlier

How to Mitigate CVE-2025-5672

Immediate Actions Required

Restrict access to the router's web management interface to trusted internal management hosts only
Disable WAN-side remote administration on all TOTOLINK N302R Plus devices
Rotate administrative credentials and enforce strong passwords to reduce the value of low-privilege access required for exploitation
Audit existing router configurations for unauthorized changes that may indicate prior exploitation

Patch Information

At the time of publication, no vendor advisory or patched firmware release for CVE-2025-5672 has been linked in public CVE references. Administrators should monitor the TOTOLINK official website for firmware updates addressing the formFilter buffer overflow. If a fixed firmware version is released, apply it to all affected N302R Plus devices and verify the version after upgrade. Where the vendor does not provide a patch, plan replacement of end-of-support hardware with currently supported equipment.

Workarounds

Place the router behind a network segment that limits HTTP access to the management interface from a dedicated administrator VLAN
Use an upstream firewall or access control list to block inbound TCP connections to the router's HTTP management port from untrusted networks
Disable any unused services on the router to reduce overall attack surface until a firmware update is available
Replace the device with a supported router model if vendor remediation is not provided within an acceptable timeframe

bash

# Configuration example: restrict management interface access using an upstream firewall
# Allow only the admin workstation subnet to reach the router's HTTP management port
iptables -A FORWARD -s 10.10.10.0/24 -d 192.168.1.1 -p tcp --dport 80 -j ACCEPT
iptables -A FORWARD -d 192.168.1.1 -p tcp --dport 80 -j DROP