CVE-2025-63154: Totolink A7000r Firmware DoS Vulnerability

CVE-2025-63154 Overview

CVE-2025-63154 is a stack overflow vulnerability discovered in the TOTOLink A7000R router firmware version 9.1.0u.6115_B20201022. The vulnerability exists in the addEffect parameter of the urldecode function, which fails to properly validate input boundaries. This flaw allows remote attackers to cause a Denial of Service (DoS) condition by sending a specially crafted POST request to the affected device.

Critical Impact
Remote attackers can crash TOTOLink A7000R routers without authentication, causing network outages and service disruption for all connected devices.

Affected Products

TOTOLink A7000R Firmware version 9.1.0u.6115_B20201022
TOTOLink A7000R Hardware Device

Discovery Timeline

2025-11-10 - CVE-2025-63154 published to NVD
2025-11-17 - Last updated in NVD database

Technical Details for CVE-2025-63154

Vulnerability Analysis

This vulnerability is classified as CWE-121 (Stack-based Buffer Overflow), a memory corruption flaw that occurs when a program writes more data to a stack-allocated buffer than it can hold. In the case of the TOTOLink A7000R, the urldecode function processes the addEffect parameter without adequate bounds checking, allowing an attacker to overflow the stack buffer with malicious input.

The vulnerability can be exploited remotely over the network without requiring any authentication or user interaction. While the immediate impact is limited to availability (DoS), stack overflow vulnerabilities in embedded devices can potentially be leveraged for more severe attacks depending on memory protections in place.

Root Cause

The root cause lies in improper input validation within the urldecode function when processing the addEffect parameter. The function allocates a fixed-size buffer on the stack to store the decoded URL data but does not verify that the incoming data fits within these boundaries. When an attacker supplies an oversized or specially crafted value for the addEffect parameter, the data overwrites adjacent memory on the stack, corrupting the execution state and causing the device to crash.

Attack Vector

The attack is executed remotely over the network through crafted HTTP POST requests. An attacker identifies a TOTOLink A7000R router on the network and sends a malicious POST request containing an oversized or specially crafted addEffect parameter. The urldecode function processes this parameter without proper bounds checking, causing a stack overflow that crashes the device. No authentication is required, and no user interaction is necessary for successful exploitation.

Technical details and proof-of-concept information are available in the GitHub Vulnerability Report.

Detection Methods for CVE-2025-63154

Indicators of Compromise

Unexpected router reboots or crashes without administrative action
Network connectivity interruptions affecting all devices on the network
Abnormal HTTP POST traffic targeting the router's web management interface
Large or malformed addEffect parameter values in HTTP request logs

Detection Strategies

Monitor network traffic for unusual POST requests to TOTOLink router management interfaces
Implement intrusion detection rules to flag oversized HTTP parameters targeting embedded device endpoints
Deploy network segmentation to isolate IoT devices and limit attack surface
Configure alerting for repeated connection attempts to router management ports

Monitoring Recommendations

Enable logging on network firewalls to capture traffic destined for router management interfaces
Set up alerts for router availability using network monitoring tools
Review HTTP access logs for anomalous parameter lengths or encoding patterns
Monitor for firmware integrity and unexpected device state changes

How to Mitigate CVE-2025-63154

Immediate Actions Required

Restrict access to the router's web management interface to trusted IP addresses only
Disable remote management if not required for operations
Implement firewall rules to block external access to the device's HTTP service
Consider placing the router behind a separate firewall or network access control device

Patch Information

At the time of publication, no official patch has been released by TOTOLink for this vulnerability. Organizations should monitor TOTOLink's official website and support channels for firmware updates addressing CVE-2025-63154. Until a patch is available, implementing the workarounds and mitigations described below is strongly recommended.

Workarounds

Restrict web management interface access to trusted internal networks only
Use firewall rules to block HTTP/HTTPS traffic to the router from untrusted sources
Disable the web management interface entirely if not needed for daily operations
Consider replacing the affected device with an alternative router if critical to network operations

bash

# Example: Restrict access to router management interface (on upstream firewall)
# Block external access to common router management ports
iptables -A INPUT -p tcp --dport 80 -s ! 192.168.1.0/24 -j DROP
iptables -A INPUT -p tcp --dport 443 -s ! 192.168.1.0/24 -j DROP