CVE-2020-29376 in V1600D
Summary
by MITRE • 11/29/2020
An issue was discovered on V-SOL V1600D V2.03.69 and V2.03.57, V1600D4L V1.01.49, V1600D-MINI V1.01.48, V1600G1 V2.0.7 and V1.9.7, and V1600G2 V1.1.4 OLT devices. There is an !j@l#y$z%x6x7q8c9z) password for the admin account to authenticate to the TELNET service.
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Analysis
by VulDB Data Team • 12/11/2020
This vulnerability represents a critical hard-coded credential flaw affecting multiple V-SOL OLT device models including V1600D, V1600D4L, V1600D-MINI, V1600G1, and V1600G2 series. The issue manifests through a well-known default password pattern that follows the format !j@l#y$z%x6x7q8c9z) which grants administrative access to the TELNET service without requiring additional authentication. This represents a fundamental security weakness that directly violates industry best practices for credential management and access control. The vulnerability exists across multiple firmware versions, indicating a persistent design flaw rather than a temporary bug that could be patched. The presence of such hard-coded credentials in network infrastructure devices creates a significant attack surface that can be exploited by malicious actors with minimal technical expertise. This flaw falls under CWE-798, which specifically addresses the use of hard-coded credentials, and represents a clear violation of the principle of least privilege that should govern all network device configurations.
The operational impact of this vulnerability extends far beyond simple unauthorized access. Attackers who discover this hard-coded credential can immediately gain administrative control over the affected OLT devices, enabling them to manipulate network configurations, intercept traffic, modify user access controls, and potentially disrupt service delivery to end users. The TELNET protocol itself presents additional security concerns as it transmits credentials and commands in plaintext, making the compromise even more dangerous when combined with the hard-coded password. This vulnerability directly maps to ATT&CK technique T1075 which covers legitimate credentials, and T1021.001 which addresses remote services through TELNET. The affected devices serve as critical network infrastructure components in telecommunications environments, making their compromise particularly damaging to network integrity and service availability.
Network administrators and security teams must immediately address this vulnerability through multiple mitigation strategies. The most critical step involves changing the default administrative password to a strong, unique credential that is properly managed through established credential lifecycle processes. Organizations should implement network segmentation to limit access to these devices and ensure that only authorized personnel can reach the TELNET service. Regular security audits should be conducted to identify any other hard-coded credentials or default accounts that may exist in the network infrastructure. The vulnerability highlights the importance of proper device provisioning and configuration management, as well as the necessity of implementing robust network access control policies. Additionally, network monitoring should be enhanced to detect unauthorized access attempts to TELNET services, and all network devices should be configured to disable unnecessary services while implementing stronger authentication mechanisms such as SSH instead of TELNET. This vulnerability serves as a stark reminder of the critical importance of proper credential management and the dangers of relying on default configurations in production network environments.