CVE-2025-6487: Totolink A3002r Buffer Overflow Vulnerability

CVE-2025-6487 Overview

CVE-2025-6487 is a stack-based buffer overflow vulnerability in the TOTOLINK A3002R router firmware version 1.1.1-B20200824.0128. The flaw resides in the formRoute function within the /boafrm/formRoute endpoint of the device's web management interface. Attackers manipulate the subnet argument to overflow a fixed-size stack buffer, corrupting adjacent memory and saved return addresses. The vulnerability is exploitable over the network and the exploit has been publicly disclosed, increasing the likelihood of opportunistic attacks against exposed devices. The weakness is categorized under [CWE-119] (Improper Restriction of Operations within the Bounds of a Memory Buffer).

Critical Impact
Remote attackers with low-privileged access can trigger memory corruption in the router's HTTP daemon, leading to denial of service or potential arbitrary code execution on the embedded device.

Affected Products

TOTOLINK A3002R router (hardware)
TOTOLINK A3002R firmware version 1.1.1-B20200824.0128
Deployments exposing the /boafrm/formRoute management endpoint

Discovery Timeline

2025-06-22 - CVE-2025-6487 published to NVD
2025-07-07 - Last updated in NVD database

Technical Details for CVE-2025-6487

Vulnerability Analysis

The vulnerability affects the formRoute handler exposed by the boa web server inside the TOTOLINK A3002R firmware. This handler processes routing configuration submissions from the device's administrative interface. The subnet parameter supplied in the HTTP request is copied into a fixed-size stack buffer without proper length validation. An attacker who can reach the web interface sends an oversized value in the subnet argument and corrupts the stack frame of formRoute.

Memory corruption in embedded router firmware often leads to control of the saved return address. On MIPS-based SOHO routers like the A3002R, this typically translates into hijacking the program counter via the ra register. Successful exploitation can yield arbitrary code execution as the user running the boa HTTP daemon, which on most TOTOLINK firmware is root.

Root Cause

The root cause is the absence of bounds checking when handling the user-controlled subnet parameter inside formRoute. The function uses unsafe string copy operations against a fixed-size stack destination, allowing input larger than the buffer to overwrite adjacent stack data. This is a classic [CWE-119] memory safety failure characteristic of legacy C code in consumer router firmware.

Attack Vector

The attack is performed remotely over HTTP against the router's web management interface. The attacker authenticates with low-privileged credentials, then issues a crafted POST request to /boafrm/formRoute with an oversized subnet parameter. Devices that expose the management interface to untrusted networks are at the greatest risk. Public proof-of-concept material has been referenced in the GitHub vulnerability documentation and VulDB entry #313595.

No verified exploit code is reproduced here. Refer to the linked advisories for technical reproduction details.

Detection Methods for CVE-2025-6487

Indicators of Compromise

HTTP POST requests to /boafrm/formRoute containing abnormally long subnet parameter values exceeding typical CIDR or dotted-quad notation length
Unexpected reboots or crashes of the router's boa web server immediately following administrative HTTP traffic
Unusual outbound connections from the router itself, suggesting post-exploitation command-and-control activity
New or modified routing entries that do not match administrator-issued changes

Detection Strategies

Inspect web server and reverse-proxy logs for requests targeting /boafrm/formRoute with parameter payloads larger than expected administrative input
Deploy network intrusion detection signatures that flag oversized subnet field submissions to TOTOLINK management endpoints
Monitor for repeated authentication attempts followed by malformed requests to formRoute, which often indicate scripted exploitation

Monitoring Recommendations

Restrict and log all access to the router's HTTP management interface using upstream firewall rules
Forward router syslog output to a centralized SIEM for correlation with broader network telemetry
Alert on management-interface traffic originating from non-administrative network segments or external sources

How to Mitigate CVE-2025-6487

Immediate Actions Required

Disable remote (WAN-side) administration on the TOTOLINK A3002R immediately
Restrict LAN-side management access to a dedicated administrative VLAN or specific trusted IP addresses
Rotate router administrative credentials, since exploitation requires authenticated access
Audit current routing tables and device configuration for unauthorized modifications

Patch Information

At the time of NVD publication on 2025-06-22, no vendor advisory or fixed firmware version is referenced in the CVE record. Administrators should monitor the TOTOLINK official website for updated firmware addressing the formRoute handler. If no patch is released, consider decommissioning the A3002R and migrating to a supported platform that receives security updates.

Workarounds

Block external access to TCP ports used by the web management interface at the perimeter firewall
Place vulnerable routers behind a network segment that is not reachable from untrusted user networks or the internet
Disable any port-forwarding or UPnP rules that expose the management interface
Replace end-of-support TOTOLINK devices when no vendor patch becomes available

bash

# Example: block external access to the router management interface
# Replace ROUTER_IP and MGMT_PORT with environment-specific values
iptables -A FORWARD -p tcp -d ROUTER_IP --dport MGMT_PORT \
  -m conntrack --ctstate NEW -j DROP