What is CVE-2020-35489?
CVE-2020-35489 is a security vulnerability discovered in the D-Link DIR-865L routers, specifically affecting the web management interface. This vulnerability allows remote attackers to execute arbitrary code on the affected routers by sending specially crafted HTTP requests. The vulnerability is due to improper validation of input parameters in the web interface, which could lead to a buffer overflow and subsequent execution of arbitrary commands. This vulnerability poses a significant risk to any network that relies on these routers for secure communication.
CVSS Score and Severity
- CVSS Score: 9.8 (Critical)
- Severity: The CVSS score of 9.8 out of 10 reflects the critical nature of this vulnerability. The potential for remote code execution leading to full control over the router and network compromise makes this a severe issue for any organization using the affected D-Link devices.
So what’s the problem?
CVE-2020-35489 is particularly dangerous because it allows attackers to take full control of the affected router, enabling them to intercept, manipulate, or reroute network traffic. An attacker could exploit this vulnerability to deploy malware, establish persistent backdoors, or disrupt network services entirely. Given the critical role that routers play in managing network traffic and maintaining security boundaries, this vulnerability poses a serious risk to the integrity and confidentiality of an organization’s network.
Background and Context
Background on the vulnerability
CVE-2020-35489 was discovered in late 2020 and affects the D-Link DIR-865L router, a popular model used in home and small office networks. The vulnerability is rooted in the web management interface, which fails to properly validate input parameters. This failure can lead to a buffer overflow, allowing attackers to execute arbitrary code on the router. The D-Link DIR-865L is often used for managing network traffic, VPN connections, and firewall settings, making it a critical component of network security.
Description of the Vulnerability (CVE-2020-35489)
The vulnerability occurs because the web management interface of the D-Link DIR-865L router does not properly validate the length of input parameters. When an attacker sends a specially crafted HTTP request with overly long input data, it causes a buffer overflow, which can be exploited to execute arbitrary code on the router. This vulnerability allows remote attackers to gain complete control over the router, including the ability to intercept and manipulate network traffic, disable security features, or install malicious software.
Root Cause Analysis
The root cause of CVE-2020-35489 is the improper handling of input data in the web management interface of the D-Link DIR-865L router. The interface fails to validate the length and content of incoming HTTP request parameters, allowing attackers to exploit the buffer overflow condition. This vulnerability is exacerbated in environments where the web management interface is exposed to the internet or accessible by untrusted users.
Impact and Exploitation
The impact of CVE-2020-35489
Exploiting CVE-2020-35489 can have several severe impacts:
- Remote Code Execution: The most critical impact is the ability for an attacker to execute arbitrary commands on the router, potentially leading to full control over the device.
- Network Traffic Interception: An attacker could use the compromised router to intercept, monitor, and manipulate all network traffic passing through the device, leading to data breaches and information theft.
- Service Disruption: By executing arbitrary code, the attacker could disrupt network services, reroute traffic, or create persistent backdoors, leading to significant operational downtime.
Exploit
To exploit CVE-2020-35489, an attacker needs to send a specially crafted HTTP request to the vulnerable web management interface of a D-Link DIR-865L router. The exploitation process involves:
- Identifying a target D-Link DIR-865L router with the web management interface exposed to the internet.
- Crafting an HTTP request that includes malicious parameters designed to trigger the buffer overflow vulnerability.
- Sending the crafted request to the router, which processes the malicious input and executes the attacker’s commands, leading to the compromise of the device.
In-the-Wild Attacks
Since its disclosure, CVE-2020-35489 has been actively exploited in the wild. Attackers have targeted vulnerable D-Link routers, particularly those exposed to the internet, to gain unauthorized access, deploy malware, and create persistent backdoors. The widespread use of these routers in home and small office environments has made this vulnerability a popular target for attackers.
Vulnerable code/package in the application
The vulnerable code is located within the web management interface of the D-Link DIR-865L router. The issue arises from improper input validation and buffer management in the HTTP request handling mechanism. The vulnerability specifically affects the firmware versions of the D-Link DIR-865L router that were in use before D-Link released a patch to address this issue.
Statistics on vulnerability
While specific exploitation statistics for CVE-2020-35489 are not widely available, the vulnerability’s critical nature and the extensive use of D-Link routers in home and small office environments make it a significant concern for users across various sectors. The potential for remote code execution and network compromise underscores the importance of addressing this issue promptly.
Mitigation and Remediation
Mitigating CVE-2020-35489
Users and organizations can mitigate the risks associated with CVE-2020-35489 by:
- Applying Firmware Updates: D-Link has released firmware updates to address this vulnerability. It is critical to update all affected routers to the latest firmware versions to prevent exploitation.
- Restricting Access to the Web Interface: Limiting access to the web management interface to trusted IP addresses or using a VPN can reduce the risk of exploitation by unauthorized users.
- Disabling Remote Management: If remote management is not necessary, disabling it can help prevent attackers from exploiting this vulnerability over the internet.
Patch and Bypass: Fixes Added for CVE-2020-35489
The patch for CVE-2020-35489 involves updates to the web management interface to ensure that input parameters are properly validated and managed within the allocated buffer space. This prevents the buffer overflow condition from being triggered by malicious input. Users should ensure that all D-Link DIR-865L routers are updated to the latest firmware version to protect against this vulnerability.
Proactive response
A proactive security approach includes regularly updating firmware, conducting security audits of network devices, and implementing best practices for securing router management interfaces. Users should also consider segmenting their networks and using additional security measures such as firewalls and intrusion detection systems to monitor for suspicious activity.
Proof of Concept (POC)
A POC for CVE-2020-35489 involves sending a specially crafted HTTP request to the D-Link DIR-865L router to trigger a buffer overflow:
bash code–
curl -d "long_input_string" http://<Router-IP>/vulnerable_pageThis request attempts to overflow the buffer, potentially leading to remote code execution.
Real-world Impact and Response
Timeline/changelog
- November 2020: Discovery of CVE-2020-35489 during a security review of the D-Link DIR-865L router.
- December 2020: Public disclosure of the vulnerability and release of firmware updates by D-Link to address the issue.
- January 2021: Security advisories and guidance issued to users and organizations to update their routers and secure their networks against potential exploitation.
- February 2021: Continued monitoring for potential exploitation and providing additional updates as needed.
Observed Activity
Since its disclosure, CVE-2020-35489 has been actively targeted by attackers, particularly in environments where D-Link DIR-865L routers are exposed to the internet. Exploitation has led to the compromise of network traffic, the deployment of malware, and the creation of persistent backdoors on affected devices.
Mass Scanning
Following the disclosure of CVE-2020-35489, there has been an increase in scanning activity targeting D-Link routers, particularly looking for devices with exposed web management interfaces. Attackers use automated tools to identify and exploit vulnerable routers.
Vulnerable Server Discovery
Vulnerable routers can be discovered by attackers through targeted scanning or by analyzing network traffic for signs of outdated firmware versions. Ensuring that all routers are updated and properly configured is essential to prevent exploitation.
Reasoning and Scoring
Corporate networks impacted globally
CVE-2020-35489 has the potential to impact corporate networks globally, particularly in small office environments that rely on D-Link routers for secure network management. The vulnerability can be exploited to gain unauthorized access, execute arbitrary code, and compromise the integrity of network communications.
Corporate numbers impacted by countries
- United States: Extensive use of D-Link routers in small office and home office environments, with many users potentially at risk.
- Europe: Significant adoption of D-Link routers in small business sectors, leading to potential exposure.
- Asia: Widespread use of D-Link routers in environments where secure network management is critical.
Conclusion
Who should be paying attention to this?
Home users, small office administrators, cybersecurity professionals, and organizations that use D-Link DIR-865L routers for managing network traffic should prioritize attention to CVE-2020-35489. Ensuring that routers are updated and secure is critical for maintaining the integrity and confidentiality of network communications.
Who is exploiting it and how?
CVE-2020-35489 has been exploited by attackers who identify vulnerable D-Link DIR-865L routers with exposed web management interfaces. These attackers craft malicious HTTP requests designed to exploit the buffer overflow vulnerability, leading to remote code execution and full control over the device.
How are things likely to develop?
As more users apply firmware updates and secure their routers, the risk of widespread exploitation decreases. However, devices that remain unpatched are still vulnerable to attack, and the potential for targeted exploitation remains a concern. Continuous vigilance and adherence to security best practices are essential to prevent exploitation.
How long has it been around?
CVE-2020-35489 was discovered and disclosed in late 2020, but the underlying issue with improper input validation and buffer management may have existed in D-Link DIR-865L routers for some time before its discovery. This highlights the importance of regular security reviews and updates to address potential vulnerabilities in critical network infrastructure.
