CVE-2024-41616: D-Link DIR-300 Auth Bypass Vulnerability

CVE-2024-41616 Overview

CVE-2024-41616 is a critical hardcoded credentials vulnerability affecting the D-Link DIR-300 REVA wireless router running firmware version 1.06B05_WW. The vulnerability exists within the device's Telnet service, which contains embedded static credentials that allow unauthorized network access to the device. This type of vulnerability (CWE-798: Use of Hard-coded Credentials, CWE-259: Use of Hard-coded Password) represents a severe security design flaw that cannot be remediated through configuration changes alone.

Critical Impact

Attackers with network access can leverage hardcoded credentials to gain full administrative control over affected D-Link DIR-300 routers, potentially compromising the entire network infrastructure and all connected devices.

Affected Products

• D-Link DIR-300 REVA (Hardware Revision A)
• D-Link DIR-300 Firmware version 1.06B05_WW
• Legacy D-Link DIR-300 series routers with vulnerable firmware

Discovery Timeline

• August 6, 2024 - CVE-2024-41616 published to NVD
• August 7, 2024 - Last updated in NVD database

Technical Details for CVE-2024-41616

Vulnerability Analysis

This vulnerability stems from the presence of hardcoded credentials embedded within the Telnet service of the D-Link DIR-300 REVA firmware. Hardcoded credentials represent a fundamental security design flaw where authentication secrets are compiled directly into the firmware binary rather than being configurable by end users. Once these credentials are discovered through firmware analysis or reverse engineering, any attacker can use them to authenticate to vulnerable devices across the internet.

The D-Link DIR-300 is a consumer-grade wireless router that has reached end-of-life status, meaning no security patches are expected from the vendor. The Telnet service, which provides command-line administrative access to the device, accepts the embedded credentials without any mechanism for users to modify or disable them. This allows complete administrative takeover of the router, including access to network configuration, traffic manipulation capabilities, and the ability to pivot to other devices on the local network.

Root Cause

The root cause of CVE-2024-41616 is the use of hardcoded authentication credentials within the firmware's Telnet service implementation. During the development process, static username and password values were embedded directly into the firmware code, violating fundamental secure coding practices. This approach to credential management is classified under CWE-798 (Use of Hard-coded Credentials) and CWE-259 (Use of Hard-coded Password), both of which are well-documented security anti-patterns.

The embedded credentials cannot be changed by device administrators, as they are compiled into the firmware binary itself. This design decision—likely made for development convenience or debugging purposes—creates a persistent backdoor that remains exploitable for the entire lifecycle of the device.

Attack Vector

The attack vector for this vulnerability is network-based, requiring the attacker to have network connectivity to the Telnet service on port 23. In many deployment scenarios, the Telnet service may be accessible from the local network, while in some misconfigured environments, it may also be exposed to the internet.

An attacker exploits this vulnerability by connecting to the Telnet service and authenticating using the hardcoded credentials. Once authenticated, the attacker gains administrative shell access to the router's underlying operating system. From this position, the attacker can modify network configurations, intercept traffic, disable security features, install persistent backdoors, or use the compromised router as a pivot point for attacks against other devices on the network.

Technical details and proof-of-concept information are available through the GitHub PoC repository and the D-Link DIR-300 documentation.

Detection Methods for CVE-2024-41616

Indicators of Compromise

• Unexpected Telnet connections to port 23 on D-Link DIR-300 devices
• Unauthorized configuration changes to router settings including DNS, firewall rules, or wireless parameters
• Presence of unknown user accounts or modified system files on the router
• Network traffic anomalies indicating the router is being used as a proxy or attack platform

Detection Strategies

• Deploy network intrusion detection systems (IDS) to monitor for Telnet authentication attempts to D-Link devices
• Implement network segmentation to isolate IoT devices and legacy routers from critical infrastructure
• Use asset discovery tools to identify D-Link DIR-300 devices running vulnerable firmware versions
• Monitor egress traffic from router management interfaces for unusual patterns

Monitoring Recommendations

• Enable logging on upstream network devices to capture connection attempts to router Telnet services
• Implement network traffic analysis to detect lateral movement originating from compromised routers
• Configure SIEM alerts for authentication events involving known IoT device IP addresses
• Regularly audit network device inventories to identify end-of-life equipment requiring replacement

How to Mitigate CVE-2024-41616

Immediate Actions Required

• Disable the Telnet service on affected D-Link DIR-300 devices if the router firmware permits this configuration
• Implement network-level access controls (firewall rules) to block external access to port 23 on affected devices
• Isolate affected routers on a separate VLAN with restricted network access
• Replace end-of-life D-Link DIR-300 devices with currently supported router hardware
• Conduct a network audit to identify all D-Link DIR-300 devices in the environment

Patch Information

The D-Link DIR-300 REVA running firmware version 1.06B05_WW has reached end-of-life status, and D-Link has not released a security patch to address this vulnerability. As hardcoded credentials are embedded in the firmware binary, the only complete remediation is hardware replacement with a currently supported device. Organizations should consult D-Link's support documentation for end-of-life product information and recommended replacement options.

Workarounds

• Block all inbound Telnet traffic (TCP port 23) at the network perimeter and on local firewalls
• Segment vulnerable devices onto isolated network segments with no internet access
• Deploy network monitoring to detect and alert on any Telnet connection attempts
• Consider implementing a VPN or jump host architecture if remote router management is required
• Document all affected devices for tracking during the hardware replacement process

# Example iptables rules to block Telnet access to affected devices
# Replace 192.168.1.1 with the actual IP of the vulnerable router

# Block external Telnet access to the router
iptables -A FORWARD -d 192.168.1.1 -p tcp --dport 23 -j DROP

# Block Telnet access from untrusted network segments
iptables -A FORWARD -s 10.0.0.0/8 -d 192.168.1.1 -p tcp --dport 23 -j DROP

# Log any Telnet connection attempts for monitoring
iptables -A INPUT -d 192.168.1.1 -p tcp --dport 23 -j LOG --log-prefix "TELNET_BLOCKED: "