CVE-2025-4823 Overview
CVE-2025-4823 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 submit-url function handled by /boafrm/formReflashClientTbl within the HTTP POST Request Handler component. Attackers can trigger the overflow remotely by sending crafted HTTP POST requests, leading to memory corruption on the affected device. The exploit details have been disclosed publicly through VulDB and a GitHub repository, increasing the risk of opportunistic exploitation against exposed devices.
Critical Impact
Remote attackers with low privileges can corrupt router memory via crafted HTTP POST requests, potentially achieving arbitrary code execution on edge networking equipment.
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-2025-4823 published to NVD
- 2026-06-17 - Last updated in NVD database
Technical Details for CVE-2025-4823
Vulnerability Analysis
The vulnerability is a classic buffer overflow [CWE-119, CWE-120] in the HTTP POST handler of the TOTOLINK boa-based web server. The /boafrm/formReflashClientTbl endpoint processes the submit-url parameter without sufficient bounds checking. When an attacker supplies an oversized value, the data overruns a fixed-size buffer in the request handler. This corrupts adjacent memory regions, including saved registers and return addresses on MIPS-based embedded hardware. Successful exploitation can result in service crash, persistent denial of service, or arbitrary code execution within the router firmware context.
Root Cause
The root cause is improper restriction of operations within the bounds of a memory buffer. The submit-url parameter handler in formReflashClientTbl lacks length validation before copying user-controlled data into a stack or heap buffer. Embedded web server binaries such as TOTOLINK's boa derivative commonly use unsafe string functions like strcpy or sprintf against attacker-supplied form fields, which is consistent with the disclosed root cause.
Attack Vector
The attack is network-based and requires low privileges, typically a session against the router's HTTP management interface. An attacker sends a POST request to /boafrm/formReflashClientTbl containing an oversized submit-url value. Devices exposing the management interface to the WAN or to untrusted LAN segments are reachable directly. Internal attackers, malicious Wi-Fi clients, or chained CSRF payloads can also deliver the request. A working proof-of-concept has been published publicly, lowering the barrier for exploitation.
No verified exploit code is included here. Refer to the GitHub PoC Repository and VulDB #309284 for technical specifics.
Detection Methods for CVE-2025-4823
Indicators of Compromise
- HTTP POST requests targeting /boafrm/formReflashClientTbl with abnormally long submit-url values.
- Unexpected reboots, crashes, or boa process restarts on TOTOLINK routers.
- New outbound connections from the router to unknown IP addresses following inbound POST traffic.
- Configuration changes or new administrative sessions not initiated by legitimate operators.
Detection Strategies
- Inspect HTTP request logs and IDS/IPS traffic for POST requests to formReflashClientTbl with payload sizes exceeding expected parameter lengths.
- Deploy network signatures that match oversized parameter values within boa-based router endpoints.
- Correlate router crash events with preceding HTTP POST activity from the same source IP.
Monitoring Recommendations
- Forward router syslog and HTTP access logs to a centralized SIEM for parameter-length anomaly analysis.
- Alert on any administrative access to the router web UI from outside expected management subnets.
- Track firmware integrity and configuration baselines on TOTOLINK devices to identify post-exploitation changes.
How to Mitigate CVE-2025-4823
Immediate Actions Required
- Disable WAN-side access to the router web administration interface immediately.
- Restrict LAN-side access to the management interface to a dedicated administrative VLAN or trusted host list.
- Reset administrator credentials and audit user accounts on each affected device.
- Inventory the network for TOTOLINK A702R, A3002R, and A3002RU devices running firmware 3.0.0-B20230809.1615.
Patch Information
No vendor patch has been published in the referenced advisories at the time of disclosure. Monitor the TOTOLINK Official Website for firmware updates addressing formReflashClientTbl. Until a fix is released, treat affected devices as untrusted edge equipment and apply the workarounds below.
Workarounds
- Block inbound access to TCP port 80/443 on the WAN interface using upstream firewall rules.
- Place affected routers behind a network segment that performs deep packet inspection on HTTP POST traffic.
- Replace end-of-life or unpatched TOTOLINK devices with vendor-supported hardware in high-risk deployments.
- Apply a web application firewall rule that drops requests to /boafrm/formReflashClientTbl with submit-url values exceeding a conservative byte limit.
# Example upstream firewall rule to block WAN access to the router web UI
iptables -A FORWARD -i wan0 -p tcp --dport 80 -d <router_ip> -j DROP
iptables -A FORWARD -i wan0 -p tcp --dport 443 -d <router_ip> -j DROP
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
