CVE-2025-54493 is a critical stack-based buffer overflow vulnerability identified in The Biosig Project's libbiosig library, specifically affecting versions 3.9.0 and the current master branch (commit 35a819fa). The vulnerability resides in the MFER (Medical Format for Electroencephalographic Recordings) file parsing functionality, particularly when processing tag 131 (0x83), which corresponds to the 'Patient Age' field. The issue occurs due to improper handling of the length parameter for this tag, where the code expects a length of exactly 7 bytes but does not adequately enforce or safely handle deviations. This leads to a buffer overflow on the stack, allowing an attacker to overwrite adjacent memory. By supplying a specially crafted MFER file with malicious content, an attacker can exploit this vulnerability to achieve arbitrary code execution without requiring any privileges or user interaction. The vulnerability is severe, with a CVSS v3.1 base score of 9.8, reflecting its network attack vector, low attack complexity, no privileges required, no user interaction, and full impact on confidentiality, integrity, and availability. The vulnerability is located in biosig.c at line 9184 in the master branch, where the parsing logic increments the buffer position without sufficient bounds checking. Although no public exploits are currently known, the critical nature and ease of exploitation make this a high-risk issue, especially in environments processing MFER files using libbiosig. Given that libbiosig is used in biomedical signal processing applications, this vulnerability could be leveraged to compromise systems handling sensitive medical data or control medical devices that rely on this library for data parsing.

For European organizations, the impact of this vulnerability is significant, particularly for healthcare providers, medical research institutions, and biomedical device manufacturers that utilize libbiosig for processing biomedical signals such as EEG data. Exploitation could lead to unauthorized code execution on systems processing MFER files, potentially resulting in data breaches involving sensitive patient information, disruption of medical services, or manipulation of medical device behavior. This could undermine patient safety, violate GDPR regulations on personal data protection, and cause operational downtime. Additionally, healthcare infrastructure is a high-value target in Europe, making this vulnerability attractive to threat actors aiming to disrupt critical services or conduct espionage. The vulnerability's network-exploitable nature means that attackers could remotely compromise systems by delivering malicious MFER files, increasing the risk of widespread impact if these files are exchanged or processed over networks. The absence of known exploits currently provides a window for mitigation, but the critical severity demands immediate attention to prevent potential future attacks.

European organizations should prioritize updating libbiosig to a patched version once available from The Biosig Project. In the interim, they should implement strict input validation and sanitization for all MFER files before processing, including verifying tag lengths and rejecting files with unexpected or malformed tags. Employing application-layer firewalls or intrusion detection systems to monitor and block suspicious MFER file transfers can reduce exposure. Restricting access to systems that process MFER files to trusted users and networks minimizes attack surface. Additionally, organizations should conduct code audits and penetration testing on applications integrating libbiosig to identify and remediate unsafe parsing logic. Deploying endpoint protection solutions capable of detecting anomalous behavior related to buffer overflow exploitation can provide further defense. Finally, maintaining robust backup and incident response plans ensures rapid recovery in case of compromise.