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January 31, 2025
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How to Mitigate CVE-2024-40891- Critical Vulnerability in Tenda AC8 Router Security
The security landscape is constantly evolving, and new vulnerabilities are discovered regularly. It is essential for security professionals to stay ahead of these threats to protect their networks and systems effectively. Recently, a critical security vulnerability, identified as CVE-2024-40891, has been discovered in the Tenda AC8 router. This vulnerability, which could lead to severe consequences if exploited, demands immediate attention and mitigation. This article aims to provide security professionals with a comprehensive understanding of the vulnerability and guide them through the necessary steps to remediate the risk. We'll delve into the technical aspects of the flaw, its impact, affected products, and, most importantly, how to fix it.
A Short Introduction to Tenda AC8 Router
The Tenda AC8 is a dual-band Gigabit WiFi router designed for home and small office use. It supports the latest WiFi standards and boasts features like MU-MIMO technology and beamforming to improve wireless coverage and performance. The router comes with a web-based interface to manage and configure network settings. While offering good functionality and value for its price, this recent vulnerability highlights the importance of staying vigilant with the security posture of networking devices. It is important to note that a compromised router can provide a backdoor into an entire network.
Summary of CVE-2024-40891
CVE ID: CVE-2024-40891
Description: A stack overflow vulnerability exists within the Tenda AC8 router firmware. This vulnerability can be exploited by sending a crafted request to the
/goform/SetFirewallCfgendpoint, specifically via thefirewallEnparameter.CVSS Score: 9.8 (Critical)
CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
The core of this vulnerability lies in the improper handling of user-supplied data within the /goform/SetFirewallCfg endpoint. The firewallEn parameter, intended to control firewall settings, is not properly validated, allowing an attacker to inject excessive data and cause a stack overflow. A stack overflow occurs when a program tries to write data beyond the boundaries of the allocated memory, potentially overwriting adjacent memory locations. In this context, an attacker could manipulate the firewallEn parameter to overwrite the return address of the function call, allowing for arbitrary code execution. Due to the critical nature of this flaw, it allows a remote unauthenticated attacker to execute code on the device which is a significant risk.
Impact of the Vulnerability
The exploitation of CVE-2024-40891 can have a severe impact on the affected Tenda AC8 routers and the networks they serve. Because of the critical CVSS score, it indicates that the vulnerability is easily exploitable and can have significant consequences. A successful exploit allows an attacker to execute arbitrary code on the router. Once code execution is achieved, the attacker could potentially:
Gain complete control of the router: This would give them access to all settings and data processed by the device.
Manipulate network traffic: The attacker could intercept, modify, or redirect network traffic, leading to man-in-the-middle attacks or denial-of-service attacks.
Establish persistent backdoors: The attacker could install malware to maintain access even after the initial exploit.
Compromise devices on the network: A compromised router can be used as an entry point to attack other devices connected to the same network.
Given these potential outcomes, it is essential for security professionals to take immediate action to mitigate the risk associated with this vulnerability.
Products Affected by the Vulnerability
The primary product affected by CVE-2024-40891 is the Tenda AC8 router, specifically the version with the following details:
|
Product
|
Version
|
Vulnerable
|
|---|---|---|
|
Tenda AC8
|
US_AC8V4.0si_V16.03.34.06_cn
|
Yes
|
It's important to note that other versions of Tenda AC8 or different Tenda models were not specifically identified as affected by the provided data, but it is advisable to monitor for new information. It is crucial for organizations that have deployed Tenda AC8 routers running the specified firmware to acknowledge this and take action to secure them against potential attacks.
How to Check Your Product is Vulnerable?
Identifying vulnerable Tenda AC8 routers is essential for remediation. Here are methods to check if your device is affected by CVE-2024-40891:
1. Firmware Version Check:
Access the router's web interface by entering its IP address in a browser.
Locate the firmware version information, typically found in the "System" or "Administration" section.
Compare the installed version with the vulnerable version
US_AC8V4.0si_V16.03.34.06_cn.
2. Network Traffic Analysis:
Monitor network traffic for unusual HTTP POST requests targeting the
/goform/SetFirewallCfgendpoint with long strings in thefirewallEnparameter.Use network analysis tools like Wireshark to capture and examine network packets.
3. Vulnerability Scanner:
Use vulnerability scanners that scan for web services, for instance, tools like
Nessus,OpenVASor other commercial scanners to detect the flaw. This will help you to detect the vulnerability in your network.
If the firmware version matches the vulnerable version or you see suspicious network activity, your device is likely affected and requires immediate attention.
How to Fix the Vulnerability?
1. Apply Firmware Updates:
The primary remediation strategy is to apply a security patch from the vendor. Monitor Tenda's official channels and their support website for announcements. Once a patch becomes available, promptly apply it.
2. Temporary Mitigation Measures
Disable Remote Access: As a temporary measure, disable remote access to the router's administration interface.
* This can be done within the router’s settings, typically under "Remote Management" or "Administration".
* Ensure that the router's management interface is only accessible from the internal network.
Firewall Rules: If remote access cannot be disabled, implement stricter firewall rules to restrict traffic to the affected endpoint.
* Block any unauthorized traffic targeting the /goform/SetFirewallCfg endpoint.
3. Input Sanitization:
If the option is available, configure a Web Application Firewall to block the malformed requests to
/goform/SetFirewallCfgendpoint.Filter the special characters in the parameter
firewallEn.
4. Network Segmentation:
Isolate vulnerable Tenda AC8 devices to a separate network segment. This will limit the potential impact if the device is compromised.
5. Monitor Network Traffic:
Continuously monitor network traffic for suspicious activity. This can help detect exploitation attempts and allow for quick incident response.
6. Regular Security Audits:
Conduct frequent security audits of network devices and update security protocols to ensure that the security posture of the devices remains consistent.
Ensure that the devices and the network are protected with the latest security tools and practices.
It's essential to implement these measures as quickly as possible to minimize the risk posed by CVE-2024-40891. A multi-layered approach that combines patching, network segmentation, and monitoring will provide the best defense. You can also read about the importance of patch management strategy, which can help you to stay secure.
By taking these steps, security professionals can effectively remediate the risk associated with CVE-2024-40891 and protect their environments against potential exploitation. It’s important to prioritize patching and follow best security practices to stay ahead of emerging threats. This vulnerability is also listed in the NVD database. A compromised router can lead to a denial of service attack, so it's very important to have a plan to prevent denial of service attacks.
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Arun KL
Arun KL is a cybersecurity professional with 15+ years of experience in IT infrastructure, cloud security, vulnerability management, Penetration Testing, security operations, and incident response. He is adept at designing and implementing robust security solutions to safeguard systems and data. Arun holds multiple industry certifications including CCNA, CCNA Security, RHCE, CEH, and AWS Security.
