CVE-2025-4834: Totolink A702R Buffer Overflow Vulnerability

CVE-2025-4834 Overview

CVE-2025-4834 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 at the endpoint /boafrm/formSetLg. An attacker can manipulate the submit-url argument to trigger a buffer overflow condition. The vulnerability is exploitable remotely over the network and the exploit has been publicly disclosed. The weakness maps to [CWE-119] (Improper Restriction of Operations within the Bounds of a Memory Buffer) and [CWE-120] (Classic Buffer Overflow).

Critical Impact
Remote attackers with low privileges can trigger memory corruption in the router's web management interface, leading to potential code execution or denial of service.

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-2025-4834 published to NVD
2025-05-23 - Last updated in NVD database

Technical Details for CVE-2025-4834

Vulnerability Analysis

The vulnerability exists in the boafrm web management binary, which handles HTTP POST requests on TOTOLINK A702R, A3002R, and A3002RU routers. The /boafrm/formSetLg handler processes the submit-url parameter without enforcing length restrictions on the supplied input. When an oversized value is submitted, the parameter data overruns the destination buffer in memory.

The EPSS score is 0.553% with a percentile of 68.47, reflecting moderate predicted exploitation likelihood. The exploit details have been disclosed publicly through VulDB and a GitHub repository, increasing the risk of opportunistic attacks against exposed devices.

Root Cause

The root cause is the absence of bounds checking when copying the user-supplied submit-url value into a fixed-size stack or heap buffer inside the formSetLg handler. SOHO router firmware frequently uses unsafe C string operations such as strcpy or sprintf on attacker-controlled HTTP parameters, which produces classic buffer overflows when input length is not validated against the destination buffer size.

Attack Vector

An attacker reaches the vulnerable endpoint over the network by sending a crafted HTTP POST request to /boafrm/formSetLg with an overlong submit-url parameter. The CVSS vector indicates that low-privileged authentication is required, meaning the attacker needs valid credentials or session access to the web interface. Devices exposing the management interface to the internet or to untrusted network segments are at the highest risk. Successful exploitation can corrupt control-flow data on the device, leading to arbitrary code execution as the web server process or device crash.

No verified proof-of-concept code is available in this dataset. See the GitHub Repository Documentation and VulDB #309300 for additional technical references.

Detection Methods for CVE-2025-4834

Indicators of Compromise

HTTP POST requests to /boafrm/formSetLg containing abnormally long submit-url parameter values.
Repeated requests to the router web management interface from a single external source.
Unexpected reboots or crashes of the boa web server process on affected TOTOLINK devices.
Outbound connections from the router to unfamiliar hosts after suspicious management traffic.

Detection Strategies

Inspect HTTP traffic to TOTOLINK routers and flag POST requests where submit-url exceeds expected length thresholds.
Deploy network IDS/IPS signatures that match oversized parameters on the /boafrm/formSetLg endpoint.
Correlate authentication events with subsequent crash or restart entries in router logs.

Monitoring Recommendations

Forward router syslog output to a central logging platform and alert on boa process termination events.
Monitor management interface access lists for unauthorized source IP addresses.
Track firmware versions across the fleet to identify devices still running 3.0.0-B20230809.1615.

How to Mitigate CVE-2025-4834

Immediate Actions Required

Restrict access to the router web management interface to trusted internal networks only.
Disable remote (WAN-side) administration on all affected TOTOLINK A702R, A3002R, and A3002RU devices.
Rotate administrator credentials, since low-privileged access is required for exploitation.
Inventory all TOTOLINK devices running firmware 3.0.0-B20230809.1615 for prioritized remediation.

Patch Information

No vendor patch is listed in the available references for CVE-2025-4834. Check the TOTOLINK Official Website for updated firmware releases addressing this issue, and review VulDB CTI ID #309300 for tracking patch availability.

Workarounds

Place affected routers behind a perimeter firewall and block inbound HTTP/HTTPS access to the management interface from untrusted networks.
Apply ACLs that restrict access to /boafrm/formSetLg to authorized management workstations only.
Consider replacing end-of-life or unsupported TOTOLINK models with actively maintained hardware if no firmware fix is published.

bash

# Example: restrict router management to a single admin subnet using iptables on an upstream gateway
iptables -A FORWARD -p tcp -d <router_ip> --dport 80 -s 192.168.10.0/24 -j ACCEPT
iptables -A FORWARD -p tcp -d <router_ip> --dport 80 -j DROP
iptables -A FORWARD -p tcp -d <router_ip> --dport 443 -s 192.168.10.0/24 -j ACCEPT
iptables -A FORWARD -p tcp -d <router_ip> --dport 443 -j DROP