CVE-2021-21739 in ZXCTN
Summary
by MITRE • 08/06/2021
A ZTE's product of the transport network access layer has a security vulnerability. Because the system does not sufficiently verify the data reliability, attackers could replace an authenticated optical module on the equipment with an unauthenticated one, bypassing system authentication and detection, thus affecting signal transmission. This affects:
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Analysis
by VulDB Data Team • 08/10/2021
The vulnerability identified as CVE-2021-21739 represents a critical security flaw in ZTE's transport network access layer products that directly impacts the integrity and authentication mechanisms of optical module management systems. This weakness stems from insufficient data reliability verification processes within the device's firmware and control software, creating a pathway for malicious actors to exploit the authentication framework. The vulnerability specifically targets the optical module validation procedures that are essential for maintaining secure communication channels in telecommunications infrastructure, where the integrity of physical components directly correlates with network security posture.
The technical exploitation of this vulnerability occurs through the manipulation of authentication protocols that govern optical module replacement operations within the transport network equipment. Attackers can substitute authenticated optical modules with unauthenticated ones without triggering system alerts or security warnings, effectively bypassing the built-in verification mechanisms. This flaw operates at the intersection of hardware authentication and software validation, where the system fails to properly validate the cryptographic signatures or authentication certificates associated with replacement modules. The vulnerability can be classified under CWE-284 Access Control Issues, specifically related to insufficient verification of module authenticity during runtime operations. According to ATT&CK framework, this represents a privilege escalation technique through hardware component manipulation, falling under T1068 Valid Accounts and T1566 Phishing for Information categories when considering the broader attack surface.
The operational impact of CVE-2021-21739 extends beyond simple authentication bypass, as it fundamentally compromises the signal transmission integrity within transport network infrastructure. When unauthorized optical modules are installed, they can introduce signal degradation, data corruption, or even complete communication failures that affect network performance and reliability. The vulnerability affects network availability and data integrity across multiple ZTE transport network access layer products, potentially disrupting critical telecommunications services including voice, data, and video transmission services. Network operators utilizing affected ZTE equipment face risks of unauthorized access to their infrastructure, potential data interception, and service disruption that could impact enterprise communications, government networks, and critical infrastructure providers. The attack vector specifically targets the module replacement process during maintenance operations, making it particularly dangerous as legitimate maintenance activities provide cover for malicious infiltration.
Mitigation strategies for this vulnerability should focus on strengthening authentication mechanisms and implementing robust verification procedures for all optical module installations. Network administrators should enforce strict change management protocols that require cryptographic verification of all replacement components, implement network monitoring systems to detect unauthorized module installations, and establish regular security audits of network access layer equipment. The implementation of secure boot mechanisms and hardware-based authentication tokens can provide additional protection layers against unauthorized module substitution. Organizations should also consider network segmentation strategies to limit the potential impact of successful exploitation and establish incident response procedures specifically designed to handle hardware-level security breaches. According to industry best practices and NIST guidelines, this vulnerability requires immediate attention through firmware updates, configuration hardening, and comprehensive security assessments of affected network infrastructure to prevent potential exploitation by threat actors targeting telecommunications networks.