CVE-2021-20132 in DIR-2640
Summary
by MITRE • 12/31/2021
Quagga Services on D-Link DIR-2640 less than or equal to version 1.11B02 use default hard-coded credentials, which can allow a remote attacker to gain administrative access to the zebra or ripd those services. Both are running with root privileges on the router (i.e., as the "admin" user, UID 0).
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Analysis
by VulDB Data Team • 01/05/2022
This vulnerability exists in D-Link DIR-2640 routers running firmware versions 1.11B02 or earlier, where the Quagga routing services contain hard-coded default credentials that can be exploited by remote attackers to obtain administrative access. The affected services include zebra and ripd routing daemons that operate with root privileges, making this a critical security flaw with significant operational impact. The vulnerability stems from poor security practices in the device's configuration where default authentication credentials are not properly changed or removed, creating a persistent backdoor for unauthorized access. This issue represents a classic example of insecure default configuration that violates fundamental security principles and allows for privilege escalation from standard user level to administrative control. The zebra and ripd services running with UID 0 privileges mean that successful exploitation would grant full system control, including the ability to modify network routing configurations, access sensitive data, and potentially compromise the entire network infrastructure.
The technical implementation of this vulnerability involves the exploitation of hardcoded credentials within the Quagga routing software package that is integrated into the D-Link router firmware. Attackers can remotely connect to the affected services using known default usernames and passwords, bypassing normal authentication mechanisms entirely. This type of vulnerability is categorized as a credential hardcoding issue that falls under CWE-259 and CWE-798, representing weaknesses where passwords or keys are embedded directly into the software source code or configuration files. The attack surface is particularly concerning because these services are typically exposed to the network and do not require additional attack vectors beyond simple credential guessing or knowledge of default values. The fact that these services run with root privileges means that exploitation results in complete system compromise, enabling attackers to execute arbitrary code, modify system files, and establish persistent access points within the network.
From an operational perspective, this vulnerability creates a significant risk for organizations relying on D-Link DIR-2640 routers for network infrastructure, as it allows for unauthorized administrative access without requiring any sophisticated attack techniques. Network administrators who have not updated their firmware or changed default credentials face a high probability of compromise, particularly in environments where these devices are exposed to external networks. The impact extends beyond simple unauthorized access to include potential network disruption, data interception, and lateral movement within the network. The vulnerability also demonstrates poor security hygiene in the device's design and deployment, as it does not implement proper authentication mechanisms or credential management practices. This flaw can be exploited by automated scanning tools that target known default credentials, making it particularly dangerous in environments where such scanning occurs regularly.
Mitigation strategies for this vulnerability should focus on immediate firmware updates from D-Link to address the hardcoded credential issue, though organizations must also implement proper network segmentation to limit exposure of affected devices to external networks. Network administrators should disable unnecessary services and ensure that all default credentials are changed immediately upon device deployment. The implementation of network monitoring solutions that can detect unauthorized access attempts to routing services provides additional defense in depth. Organizations should also conduct regular vulnerability assessments to identify other devices with similar hardcoded credential issues and ensure proper access controls are implemented. This vulnerability highlights the importance of following security best practices such as the principle of least privilege, proper credential management, and regular security updates. The ATT&CK framework categorizes this as a privilege escalation technique through default credentials, emphasizing the need for robust authentication controls and continuous monitoring of network access patterns. Additionally, organizations should consider implementing network access control lists and firewall rules to restrict access to routing services to only trusted administrative networks.