CVE-2025-54489 is a critical stack-based buffer overflow vulnerability identified in The Biosig Project's libbiosig library, specifically affecting versions 3.9.0 and the Master Branch (commit 35a819fa). The vulnerability arises in the MFER (Multi-File EEG Recording) parsing functionality, where the code improperly handles the length of data read from specially crafted MFER files. The vulnerable code segment reads a length value (len2) from the input file, which can be up to 255 bytes, but copies this data into a fixed-size buffer 'buf' of only 128 bytes without adequate bounds checking. This discrepancy allows an attacker to overflow the stack buffer by providing a maliciously crafted MFER file with an oversized len2 value. The overflow can lead to arbitrary code execution, compromising the confidentiality, integrity, and availability of the affected system. The vulnerability does not require any authentication or user interaction, and can be triggered remotely by supplying a malicious file to an application or system component that uses libbiosig for MFER file parsing. The CVSS v3.1 base score is 9.8 (critical), reflecting the high impact and ease of exploitation. No known public exploits are reported yet, but the severity and nature of the flaw make it a significant threat once weaponized. The root cause is a classic CWE-121 stack-based buffer overflow due to improper input validation and unsafe memory operations in biosig.c at line 8970, specifically when processing tag 63 in the MFER file format.

For European organizations, this vulnerability poses a severe risk particularly to those in healthcare, neuroscience research, and any sector relying on biosignal processing software that incorporates libbiosig for EEG or related data analysis. Exploitation could lead to remote code execution, enabling attackers to take full control of affected systems, steal sensitive medical or research data, disrupt critical services, or use compromised systems as footholds for lateral movement within networks. Given the critical nature of healthcare infrastructure in Europe and stringent data protection regulations like GDPR, a breach resulting from this vulnerability could lead to significant operational disruption, financial penalties, and reputational damage. Additionally, research institutions and companies developing neurotechnology or brain-computer interfaces could face intellectual property theft or sabotage. The vulnerability’s ability to be triggered without authentication or user interaction increases the risk of automated or targeted attacks, potentially impacting a wide range of organizations that process MFER files or use libbiosig indirectly through dependent software.

1. Immediate upgrade or patching: Organizations should monitor The Biosig Project for official patches or updates addressing CVE-2025-54489 and apply them promptly. If no patch is available, consider temporarily disabling MFER file parsing or replacing libbiosig with alternative libraries that do not have this vulnerability. 2. Input validation and sandboxing: Implement strict validation of MFER files before processing, including size and format checks to detect malformed or suspicious files. Run biosig-dependent applications in sandboxed or isolated environments with minimal privileges to limit the impact of potential exploitation. 3. Network and file access controls: Restrict the sources from which MFER files can be received, especially from untrusted networks or users. Employ network segmentation and file integrity monitoring to detect and block malicious files. 4. Code review and static analysis: For organizations maintaining forks or custom versions of libbiosig, conduct thorough code audits focusing on buffer management and input handling to identify and remediate similar vulnerabilities. 5. Incident response readiness: Prepare detection signatures and response plans for potential exploitation attempts, including monitoring for anomalous process behavior or unexpected code execution in systems using libbiosig.