CVE-2025-4827: Totolink A702r Buffer Overflow Vulnerability

CVE-2025-4827 Overview

CVE-2025-4827 is a buffer overflow vulnerability affecting TOTOLINK A702R, A3002R, and A3002RU routers running firmware version 3.0.0-B20230809.1615. The flaw resides in an unknown function within the /boafrm/formSaveConfig endpoint of the HTTP POST Request Handler. Attackers can manipulate the submit-url argument to overflow a fixed-size buffer. The vulnerability is exploitable remotely over the network and requires only low-level privileges. The exploit details have been publicly disclosed, increasing the risk of opportunistic attacks against exposed devices.

Critical Impact
Remote attackers can trigger a buffer overflow in the router's web management interface, potentially leading to arbitrary code execution or denial of service on affected TOTOLINK devices.

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-2025-4827 published to NVD
2026-06-17 - Last updated in NVD database

Technical Details for CVE-2025-4827

Vulnerability Analysis

The vulnerability is classified under [CWE-119] (Improper Restriction of Operations within the Bounds of a Memory Buffer) and [CWE-120] (Classic Buffer Overflow). The flaw exists in the /boafrm/formSaveConfig handler, a component of the BOA web server commonly embedded in TOTOLINK firmware. When an HTTP POST request supplies the submit-url parameter, the handler copies the value into a fixed-size stack buffer without sufficient length validation. An attacker with a valid session can submit an oversized submit-url value to corrupt adjacent stack memory.

Successful exploitation results in confidentiality, integrity, and availability impact on the affected device. The EPSS score of 0.661% reflects current exploitation likelihood based on public indicators.

Root Cause

The root cause is unsafe handling of user-controlled HTTP POST parameters. The formSaveConfig function uses unsafe string copy operations such as strcpy or sprintf against the submit-url value without validating its length against the destination buffer size. This pattern is recurrent across TOTOLINK BOA-derived web management interfaces.

Attack Vector

The attack vector is network-based. An attacker sends a crafted HTTP POST request to /boafrm/formSaveConfig with an oversized submit-url parameter. The router parses the request and overflows the destination buffer during configuration save processing. Depending on memory layout and any mitigations present on the MIPS or ARM firmware build, the overflow can corrupt the return address and redirect execution to attacker-controlled shellcode. At minimum, the overflow crashes the web service and forces a reboot.

The vulnerability requires low privileges, meaning an authenticated session to the device's web interface is needed. Devices with default or weak credentials exposed to the internet face elevated risk.

Detection Methods for CVE-2025-4827

Indicators of Compromise

Unexpected reboots or crashes of the TOTOLINK web management daemon (boa or goahead process)
HTTP POST requests to /boafrm/formSaveConfig containing abnormally long submit-url parameter values
Source IP addresses repeatedly accessing the router admin interface from external networks
Modifications to router configuration files made outside of administrator change windows

Detection Strategies

Inspect web server access logs on the router for POST requests to /boafrm/formSaveConfig with payload lengths exceeding normal configuration sizes
Deploy network IDS signatures that match oversized submit-url parameters in HTTP requests directed at TOTOLINK management ports
Monitor for repeated authentication attempts followed by anomalous POST traffic to the admin interface

Monitoring Recommendations

Forward router syslog data to a central logging platform for correlation against authentication and configuration events
Alert on any administrative HTTP traffic originating from outside management networks
Track firmware version and configuration baselines across deployed TOTOLINK devices to detect drift after suspected exploitation

How to Mitigate CVE-2025-4827

Immediate Actions Required

Restrict access to the router's web management interface to trusted internal management networks only
Disable remote (WAN-side) administration on affected TOTOLINK A702R, A3002R, and A3002RU devices
Replace default administrator credentials with strong unique passwords to limit unauthenticated reachability of the vulnerable handler
Inventory all TOTOLINK devices running firmware 3.0.0-B20230809.1615 and prioritize them for remediation

Patch Information

No vendor patch is referenced in the available advisories at the time of publication. Refer to the TOTOLINK Official Website for firmware updates and the VulDB advisory for tracking remediation status. Technical disclosure details are available in the GitHub disclosure repository.

Workarounds

Place the router behind a network firewall that blocks inbound HTTP/HTTPS access to the management interface
Segment IoT and consumer-grade networking equipment from production and user networks
Consider replacing end-of-support TOTOLINK models with actively maintained networking hardware if no firmware fix is released

bash

# Example iptables rule to restrict router admin access to a management subnet
iptables -A INPUT -p tcp --dport 80 -s 192.168.10.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 80 -j DROP