CVE-2020-29324 in DIR-895L MFC
Summary
by MITRE • 06/05/2021
The DLink Router DIR-895L MFC v1.21b05 is vulnerable to credentials disclosure in telnet service through decompilation of firmware, that allows an unauthenticated attacker to gain access to the firmware and to extract sensitive data.
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Analysis
by VulDB Data Team • 06/10/2021
The CVE-2020-29324 vulnerability affects the D-Link DIR-895L MFC router firmware version 1.21b05, presenting a critical security flaw in the telnet service implementation. This vulnerability stems from insufficient protection mechanisms within the device's firmware that allow unauthorized access to sensitive credentials through firmware decompilation techniques. The issue represents a fundamental failure in the router's security architecture, where authentication mechanisms are bypassed through reverse engineering approaches that exploit weak cryptographic practices and inadequate credential storage methods.
The technical exploitation of this vulnerability involves decompiling the router's firmware image to extract hardcoded credentials or authentication parameters that are improperly stored within the device's software components. This type of attack falls under the category of firmware-level attacks that leverage the principle of least privilege violation, where sensitive information should not be exposed through readily accessible firmware analysis. The vulnerability specifically targets the telnet service configuration, which typically operates with elevated privileges and requires robust authentication mechanisms to prevent unauthorized access to administrative functions.
From an operational perspective, this vulnerability creates significant risks for network security and compliance requirements. An unauthenticated attacker who successfully extracts credentials can gain full administrative access to the router configuration, potentially leading to complete network compromise. The impact extends beyond simple credential theft as it enables attackers to modify firewall rules, change network configurations, redirect traffic, and establish persistent backdoors within the network infrastructure. This vulnerability directly violates security principles outlined in the NIST Cybersecurity Framework and represents a failure in the device's security-by-design approach.
The exploitation of this vulnerability aligns with several ATT&CK framework techniques including T1219 - Remote Access Software and T1552.001 - Unsecured Credentials, demonstrating how firmware-level weaknesses can be leveraged to achieve persistent access to network infrastructure. Organizations using affected D-Link devices face potential compliance violations under standards such as ISO 27001 and NIST SP 800-53, which require proper credential management and secure configuration practices. The vulnerability also relates to CWE-312 (Cleartext Storage of Sensitive Information) and CWE-316 (Cleartext Storage of Sensitive Information in Memory) categories, indicating that sensitive data is stored in an easily accessible format within the firmware.
Mitigation strategies should include immediate firmware updates from D-Link to address the credential exposure issue, implementation of network segmentation to limit access to administrative interfaces, and disabling unnecessary services such as telnet when not required for legitimate operations. Organizations should also conduct comprehensive vulnerability assessments of their network infrastructure to identify similar firmware-level vulnerabilities and implement robust firmware integrity checking mechanisms. Additionally, the use of secure credential management practices, including regular credential rotation and enforcement of strong authentication mechanisms, should be implemented to reduce the impact of potential credential exposure incidents. The vulnerability highlights the importance of secure firmware development practices and proper security testing during the device lifecycle to prevent similar issues in future deployments.