CVE-2017-14422 in DIR-850L
Summary
by MITRE
D-Link DIR-850L REV. A (with firmware through FW114WWb07_h2ab_beta1) and REV. B (with firmware through FW208WWb02) devices use the same hardcoded /etc/stunnel.key private key across different customers' installations, which allows remote attackers to defeat the HTTPS cryptographic protection mechanisms by leveraging knowledge of this key from another installation.
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Analysis
by VulDB Data Team • 11/15/2019
The vulnerability identified as CVE-2017-14422 represents a critical cryptographic weakness in D-Link DIR-850L router models across multiple firmware revisions. This issue stems from the implementation of a hardcoded private key within the stunnel configuration, specifically located at /etc/stunnel.key, which is shared across all affected devices regardless of their individual customer installations. The flaw demonstrates a fundamental failure in cryptographic key management practices and violates core security principles governing the uniqueness of cryptographic materials. This vulnerability affects both revision A and B models of the DIR-850L device, with the issue persisting through specific firmware versions including FW114WWb07_h2ab_beta1 for revision A and FW208WWb02 for revision B, indicating a widespread and persistent problem within the product line.
The technical exploitation of this vulnerability occurs through a well-defined attack vector that leverages the predictable nature of the hardcoded private key. When remote attackers obtain knowledge of this shared private key from one customer installation, they can subsequently decrypt HTTPS traffic destined for other customers' devices that utilize the same firmware version. This compromise undermines the fundamental security guarantees provided by HTTPS encryption, allowing attackers to intercept, modify, or inject malicious data within the encrypted communication channels. The vulnerability directly maps to CWE-326, which describes the weakness of using insufficiently random values in cryptographic operations, and specifically relates to the improper handling of cryptographic keys within network infrastructure devices. The attack methodology follows established patterns described in the MITRE ATT&CK framework under the technique of credential access through the exploitation of weak cryptographic implementations.
The operational impact of this vulnerability extends far beyond simple privacy concerns, as it fundamentally compromises the integrity of secure communications within affected networks. Organizations relying on these routers for network security face significant risks including data exfiltration, man-in-the-middle attacks, and potential network infiltration through compromised encrypted channels. The shared nature of the private key across multiple installations means that a single compromise can expose numerous customer networks simultaneously, creating cascading security failures that can be difficult to contain and remediate. This vulnerability particularly affects enterprise and home network environments where HTTPS traffic is commonly used for sensitive communications, including financial transactions, personal data transfers, and administrative access to network resources. The impact is exacerbated by the fact that many users may not be aware of the compromised encryption, leading to prolonged exposure periods without active detection mechanisms.
Mitigation strategies for this vulnerability require immediate action to address the hardcoded key issue and implement proper cryptographic key management practices. Network administrators should prioritize firmware updates from D-Link to resolve the hardcoded key problem, though the vulnerability's nature suggests that even updated firmware may require additional security hardening. The recommended approach involves implementing unique cryptographic keys for each device installation, following the principle of least privilege in cryptographic material distribution. Security teams should conduct comprehensive network assessments to identify all affected devices and implement monitoring solutions to detect potential exploitation attempts. Additional protective measures include network segmentation to limit the scope of potential attacks, enhanced intrusion detection systems, and regular security audits to ensure proper key management practices are maintained. The vulnerability highlights the critical importance of proper key lifecycle management as outlined in industry standards such as NIST SP 800-57 and ISO/IEC 14443, which emphasize the need for unique cryptographic materials in network security implementations.