CVE-2025-4831: Totolink A702r Buffer Overflow Vulnerability

CVE-2025-4831 Overview

CVE-2025-4831 is a buffer overflow vulnerability affecting TOTOLINK A702R, A3002R, and A3002RU routers running firmware version 3.0.0-B20230809.1615. The flaw resides in the HTTP POST request handler for the /boafrm/formSiteSurveyProfile endpoint. Attackers can manipulate the submit-url argument to overflow a fixed-size buffer in the boa web server process. The exploit has been publicly disclosed, increasing the risk of opportunistic abuse against exposed devices. Successful exploitation can lead to arbitrary code execution or denial of service on affected routers [CWE-119, CWE-120].

Critical Impact
Remote attackers with low-privileged access can trigger a buffer overflow in the router web interface, enabling code execution or service disruption on the device.

Affected Products

TOTOLINK A702R firmware 3.0.0-B20230809.1615
TOTOLINK A3002R firmware 3.0.0-B20230809.1615
TOTOLINK A3002RU firmware 3.0.0-B20230809.1615

Discovery Timeline

2025-05-17 - CVE-2025-4831 published to NVD
2026-06-17 - Last updated in NVD database

Technical Details for CVE-2025-4831

Vulnerability Analysis

The vulnerability affects the boa HTTP server used by TOTOLINK routers to render the web management interface. The handler for /boafrm/formSiteSurveyProfile parses POST parameters from administrative requests but fails to validate the length of the submit-url argument before copying it into a fixed-size stack buffer. An attacker who submits an oversized value triggers a classic stack-based buffer overflow, corrupting adjacent memory and potentially the saved return address. Because the router firmware runs without modern memory protections such as stack canaries or ASLR, the overflow can be steered into arbitrary code execution within the web server context.

Root Cause

The root cause is missing bounds checking on user-supplied input in the formSiteSurveyProfile POST handler. The function uses an unsafe string copy operation that trusts the length of submit-url from the client request. This pattern, classified under [CWE-120] (Buffer Copy without Checking Size of Input), allows an attacker to write beyond the intended buffer boundary.

Attack Vector

Exploitation occurs remotely over the network against the router's HTTP management interface. The attacker sends a crafted POST request to /boafrm/formSiteSurveyProfile containing an overlong submit-url parameter. Authenticated low-privilege access to the web interface is required, but TOTOLINK consumer routers frequently ship with weak or default credentials. Once exploited, the attacker can disrupt router operation or hijack execution flow. Detailed technical analysis is available in the GitHub disclosure and the VulDB entry.

Detection Methods for CVE-2025-4831

Indicators of Compromise

HTTP POST requests to /boafrm/formSiteSurveyProfile containing abnormally long submit-url parameter values.
Unexpected boa web server crashes, restarts, or core dumps on affected TOTOLINK routers.
Outbound connections from the router to unknown command-and-control infrastructure following administrative interface activity.

Detection Strategies

Inspect network traffic to router management interfaces for POST requests targeting /boafrm/formSiteSurveyProfile with parameter lengths exceeding typical bounds.
Correlate authentication events to the router web UI with subsequent service instability or unexplained configuration changes.
Deploy signature-based intrusion detection rules that match oversized submit-url values in HTTP POST payloads to the affected endpoint.

Monitoring Recommendations

Log and review all administrative access attempts to TOTOLINK router web interfaces, prioritizing access from non-management network segments.
Monitor router DNS queries and outbound flows for indicators of post-exploitation activity such as botnet beaconing.
Track firmware version inventory across deployed TOTOLINK devices to identify hosts still running 3.0.0-B20230809.1615.

How to Mitigate CVE-2025-4831

Immediate Actions Required

Restrict access to the router web management interface to trusted internal management VLANs and block WAN-side administration.
Replace default and weak administrative credentials with strong, unique passwords to reduce the likelihood of authenticated exploitation.
Inventory affected TOTOLINK A702R, A3002R, and A3002RU devices running firmware 3.0.0-B20230809.1615 and isolate them pending remediation.

Patch Information

At the time of publication, no vendor advisory or patched firmware has been released by TOTOLINK for CVE-2025-4831. Administrators should monitor the TOTOLINK official site for firmware updates and apply them immediately upon availability.

Workarounds

Disable remote (WAN) management on affected routers to prevent internet-based exploitation attempts.
Place TOTOLINK devices behind a network firewall that filters access to TCP/80 and TCP/443 management ports from untrusted networks.
Replace end-of-support TOTOLINK consumer routers with hardware that receives active security maintenance if a firmware fix is not forthcoming.

bash

# Example: block external access to the router management interface using iptables
iptables -A INPUT -i wan0 -p tcp --dport 80 -j DROP
iptables -A INPUT -i wan0 -p tcp --dport 443 -j DROP