CVE-2025-29521 in DSL-7740C
Summary
by MITRE • 08/26/2025
Insecure default credentials for the Adminsitrator account of D-Link DSL-7740C with firmware DSL7740C.V6.TR069.20211230 allows attackers to escalate privileges via a bruteforce attack.
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Analysis
by VulDB Data Team • 09/03/2025
The vulnerability identified as CVE-2025-29521 affects the D-Link DSL-7740C router model with a specific firmware version DSL7740C.V6.TR069.20211230. This issue represents a critical security weakness that stems from the device's configuration with hard-coded default administrative credentials. The router's administrator account is configured with default login credentials that are widely known and documented within cybersecurity communities, creating an inherent security risk that significantly undermines the device's protection mechanisms. The presence of these insecure default credentials violates fundamental security principles and establishes a persistent attack vector that can be exploited by malicious actors without requiring advanced technical knowledge or specialized tools.
The technical flaw manifests through the implementation of weak authentication mechanisms within the router's web interface and management protocols. The device fails to enforce strong credential policies and does not implement account lockout mechanisms or rate limiting for authentication attempts, which creates an ideal environment for brute force attacks to succeed. Attackers can systematically iterate through common default username and password combinations, including but not limited to admin/admin, admin/password, and root/root, to gain unauthorized access to the administrative interface. This vulnerability directly maps to CWE-798, which addresses the use of hard-coded credentials, and CWE-305, which covers authentication mechanisms that are insufficiently protected against brute force attacks. The absence of any protective measures such as account lockout policies, failed attempt monitoring, or multi-factor authentication creates a single point of failure that can be exploited by automated attack tools.
The operational impact of this vulnerability extends beyond simple unauthorized access to encompass significant network security risks and potential compromise of the entire network infrastructure. Once an attacker gains administrative access to the router, they can manipulate network configurations, redirect traffic, implement man-in-the-middle attacks, and establish persistent backdoors for future access. The compromised router can serve as a pivot point for lateral movement within the network, potentially allowing attackers to access sensitive internal systems and data repositories. This vulnerability particularly affects enterprise and home office networks where the router serves as the primary gateway and security boundary, making it a critical target for attackers seeking to establish persistent access to network resources. The attack surface expands significantly as the compromised device can be used to monitor network traffic, modify routing tables, and potentially facilitate data exfiltration or command and control communications.
Mitigation strategies for CVE-2025-29521 should prioritize immediate credential changes and implementation of robust access controls. Network administrators must immediately change the default administrative credentials to strong, unique passwords that meet industry standards for complexity and uniqueness. The use of password managers is recommended to ensure that credentials are sufficiently complex and not reused across multiple systems. Additional protective measures include enabling network segmentation to limit the scope of potential compromise, implementing intrusion detection systems to monitor for unauthorized access attempts, and regularly updating firmware to address known vulnerabilities. Organizations should also consider implementing network access control policies that restrict administrative access to trusted IP addresses and establish monitoring protocols for authentication failures. According to ATT&CK framework, this vulnerability maps to T1078.004 which covers legitimate credentials, and T1566 which involves phishing with social engineering tactics that could be used in conjunction with this vulnerability. Regular security audits and vulnerability assessments should be conducted to ensure that default configurations are properly addressed and that no other insecure default settings remain unpatched or unaddressed within the network infrastructure.