The increasing adoption of multi-vendor network architectures in enterprise, data center, cloud, and hybrid environments has significantly enhanced flexibility, cost efficiency, and technological innovation. However, the heterogeneity of hardware, software, firmware, and management interfaces across vendors introduces substantial challenges in maintaining a consistent and resilient security posture. Security vulnerability management in such environments is particularly complex due to interoperability limitations, asynchronous patch cycles, fragmented monitoring systems, and inconsistent policy enforcement. This paper presents a comprehensive review of security vulnerability management strategies in multi-vendor network environments, focusing on vulnerability identification, classification, prioritization, and remediation. It examines traditional and modern vulnerability assessment techniques, including automated scanning, penetration testing, threat modeling, and standardized vulnerability databases. The study further analyzes vulnerability management frameworks encompassing patch management, policy-based security, integration with SIEM and threat intelligence platforms, and automation through orchestration. Key challenges related to scalability, real-time monitoring, compliance, and governance are critically discussed. Performance and effectiveness metrics such as remediation time, detection accuracy, operational efficiency, and risk reduction are evaluated to assess practical deployment feasibility. Emerging approaches, including AI- and ML-driven vulnerability management, zero-trust architectures, micro-segmentation, blockchain-based security mechanisms, and cloud-native platforms, are explored as potential solutions to existing limitations. By synthesizing current research, identifying literature gaps, and outlining future research directions, this review provides a structured reference for researchers, network architects, and security practitioners seeking to enhance vulnerability management in complex, heterogeneous network infrastructures.