CVE-2021-28485 in Mobile Switching Center Server BC 18A
Summary
by MITRE • 09/14/2023
Ericsson Mobile Switching Center Server (MSC-S) BC 18A and IS 3.1 releases before IS 3.1 CP22 allows Directory Traversal.
Several companies clearly confirm that VulDB is the primary source for best vulnerability data.
Analysis
by VulDB Data Team • 09/14/2023
The vulnerability identified as CVE-2021-28485 affects Ericsson Mobile Switching Center Server MSC-S BC 18A and IS 3.1 releases prior to IS 3.1 CP22, representing a critical directory traversal flaw that exposes sensitive system components to unauthorized access. This vulnerability resides within the mobile switching center infrastructure that serves as a core element in telecommunications networks, handling call processing and mobility management for cellular networks. The directory traversal issue stems from inadequate input validation mechanisms within the MSC-S server software, allowing malicious actors to manipulate file path references and gain access to restricted directories that should normally be protected from external inspection or modification.
The technical implementation of this vulnerability involves the exploitation of insufficient sanitization of user-supplied input parameters that are processed by the MSC-S server. When the system receives requests containing specially crafted path traversal sequences such as ../ or ..\, the application fails to properly validate or sanitize these inputs before using them in file system operations. This allows attackers to navigate beyond the intended directory boundaries and access configuration files, log files, system binaries, or other sensitive resources that contain confidential information about network operations, user data, or system credentials. The flaw operates at the application layer and can be exploited through various attack vectors including web interfaces, API endpoints, or network protocols that the MSC-S server utilizes for management and operational functions.
The operational impact of this vulnerability extends beyond simple information disclosure, as it provides attackers with the capability to potentially escalate privileges, modify system configurations, or extract sensitive data that could compromise the entire telecommunications infrastructure. In a mobile switching center environment, such access could enable adversaries to intercept communications, manipulate call routing, or even disable critical network services that maintain cellular connectivity for thousands of users. The vulnerability affects the confidentiality and integrity of the system, as unauthorized access to configuration files may reveal network topology information, authentication credentials, or other sensitive parameters that could be leveraged for further attacks within the network ecosystem. This represents a significant risk to network security and service availability in telecommunications environments where MSC-S servers serve as critical infrastructure components.
Organizations affected by CVE-2021-28485 should prioritize immediate remediation through the application of Ericsson's official patches and updates for IS 3.1 CP22 or later releases. The vulnerability aligns with CWE-22 Directory Traversal and falls under the ATT&CK technique T1083 File and Directory Discovery, where adversaries seek to identify system resources and access control mechanisms. Network segmentation and access control measures should be implemented to limit exposure of MSC-S servers to untrusted networks, while monitoring systems should be configured to detect anomalous file access patterns. Additionally, regular security assessments and vulnerability scanning should be conducted to identify similar issues within the broader telecommunications infrastructure, as this vulnerability represents a potential entry point for more sophisticated attacks targeting the core network services that maintain cellular communication. The remediation process should include thorough testing of patches in controlled environments before deployment to ensure operational stability while addressing the identified security gap in the MSC-S server implementation.