CVE-2025-9780 Overview
CVE-2025-9780 is a buffer overflow vulnerability in the TOTOLINK A702R router firmware version 4.0.0-B20211108.1423. The flaw resides in the sub_419BE0 function within the /boafrm/formIpQoS endpoint. Attackers can trigger the overflow by manipulating the mac argument supplied to this handler. The issue is remotely exploitable and a public proof-of-concept has been released, increasing the risk of opportunistic attacks against exposed devices. The vulnerability 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 corrupt memory in the embedded web server, leading to potential code execution or denial of service against the router.
Affected Products
- TOTOLINK A702R router hardware
- TOTOLINK A702R firmware version 4.0.0-B20211108.1423
- Deployments exposing the /boafrm/formIpQoS web interface to untrusted networks
Discovery Timeline
- 2025-09-01 - CVE-2025-9780 published to the National Vulnerability Database
- 2025-09-04 - Last updated in NVD database
Technical Details for CVE-2025-9780
Vulnerability Analysis
The vulnerability exists in the TOTOLINK A702R router firmware's HTTP handler for Quality-of-Service configuration. The function sub_419BE0, invoked when processing requests to /boafrm/formIpQoS, fails to enforce bounds on the mac parameter supplied by the client. When an oversized string is copied into a fixed-size stack or heap buffer, adjacent memory regions are overwritten, corrupting program control data such as saved return addresses or function pointers.
Because the BOA-based web server runs with elevated privileges typical for embedded Linux router firmware, successful memory corruption can be leveraged to hijack execution flow. The attack surface is reachable over the network and does not require user interaction. Public technical analysis and proof-of-concept payloads are available in the rew1X GitHub PoC repository.
Root Cause
The root cause is the absence of length validation on the mac parameter before it is processed by sub_419BE0. The function uses unsafe string-handling routines that copy attacker-controlled input into a fixed-size buffer, an instance of CWE-119. The MAC address field is expected to follow a strict 17-character format, but the firmware does not reject inputs that exceed this length.
Attack Vector
An attacker submits a crafted HTTP request to the /boafrm/formIpQoS endpoint with an oversized mac parameter. The request can be issued from any network position that can reach the router's management interface, including the LAN side or the WAN side when remote administration is enabled. Authentication is required at a low privilege level. Refer to the VulDB entry #322082 and the PoC demonstration for the exact request structure used to trigger the overflow.
Detection Methods for CVE-2025-9780
Indicators of Compromise
- HTTP POST requests to /boafrm/formIpQoS containing a mac parameter exceeding the expected 17-character MAC address format.
- Unexpected reboots, crashes, or service restarts of the BOA web server process on TOTOLINK A702R devices.
- Outbound connections from the router to unfamiliar hosts following inbound QoS configuration requests.
Detection Strategies
- Inspect web server access logs for malformed mac parameter values targeting the formIpQoS handler.
- Deploy network-based intrusion detection signatures that flag oversized POST payloads to TOTOLINK management endpoints.
- Baseline router CPU and memory consumption to detect anomalies indicative of exploitation attempts.
Monitoring Recommendations
- Forward syslog from edge routers to a centralized logging platform for correlation and retention.
- Monitor for repeated authentication events followed by HTTP requests to QoS configuration paths.
- Alert on any external sources attempting to access the router's administrative interface.
How to Mitigate CVE-2025-9780
Immediate Actions Required
- Disable remote (WAN-side) administration of the TOTOLINK A702R web interface immediately.
- Restrict LAN access to the management interface using firewall rules or a dedicated management VLAN.
- Rotate administrative credentials and audit existing accounts for unauthorized changes.
- Consider replacing end-of-life or unpatched TOTOLINK A702R devices with currently supported router hardware.
Patch Information
No official vendor patch has been published in the references associated with CVE-2025-9780 at the time of publication. Monitor the TOTOLINK official website for firmware updates addressing the formIpQoS handler. Until a fix is released, apply the compensating controls described below.
Workarounds
- Block external access to TCP ports used by the router's HTTP management interface at the upstream firewall.
- Apply network segmentation to isolate vulnerable routers from sensitive internal assets.
- Filter inbound HTTP requests to /boafrm/formIpQoS at a reverse proxy or web application firewall where feasible.
- Disable the QoS feature in the router configuration if it is not actively required.
# Example iptables rules to restrict access to the router management interface
iptables -A INPUT -p tcp --dport 80 -s 192.168.1.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 80 -j DROP
iptables -A INPUT -p tcp --dport 443 -s 192.168.1.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 443 -j DROP
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
