CVE-2025-54491 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 arises in the MFER (Medical Format for Electroencephalographic Recordings) parsing functionality, which is responsible for processing patient event data within biosig.c source code. The flaw occurs at line 9191 when the parser encounters a tag value of 65 (0x41), corresponding to patient event data. The vulnerable code increments a buffer position pointer (curPos) by reading data from a buffer without adequate bounds checking, allowing a specially crafted MFER file to overflow the stack buffer. This overflow can lead to arbitrary code execution, enabling an attacker to execute malicious payloads remotely without requiring authentication or user interaction. The CVSS v3.1 base score of 9.8 reflects the vulnerability's high severity, with network attack vector, low attack complexity, no privileges required, and no user interaction needed, impacting confidentiality, integrity, and availability. Although no known exploits are reported in the wild yet, the vulnerability's nature and ease of exploitation make it a significant threat, especially to systems processing medical EEG data using libbiosig. The Biosig Project is widely used in biomedical signal processing applications, research institutions, and healthcare environments, making this vulnerability particularly relevant to medical device software and clinical data analysis tools that rely on libbiosig for MFER file parsing.

For European organizations, the impact of CVE-2025-54491 is substantial, particularly for healthcare providers, medical research institutions, and biomedical device manufacturers that utilize libbiosig for EEG and other biosignal data processing. Exploitation could lead to unauthorized code execution on critical systems handling sensitive patient data, resulting in potential breaches of patient confidentiality, data manipulation, and disruption of medical services. This could compromise the integrity of diagnostic data, leading to misdiagnosis or treatment errors. Additionally, availability impacts could disrupt clinical workflows and delay patient care. Given the strict regulatory environment in Europe, including GDPR and medical device regulations, organizations face significant compliance risks and potential legal liabilities if patient data is compromised. The vulnerability also poses risks to research institutions that rely on biosignal data for clinical studies, potentially undermining research integrity and intellectual property. The absence of known exploits in the wild provides a window for proactive mitigation, but the critical severity necessitates immediate attention to prevent targeted attacks.

To mitigate CVE-2025-54491, European organizations should take the following specific actions: 1) Immediately update libbiosig to a patched version once released by The Biosig Project. In the absence of an official patch, consider applying temporary source code mitigations such as adding strict bounds checking around the MFER parsing code, especially for tag 65 processing. 2) Implement strict input validation and sanitization for all MFER files before processing, including file integrity checks and size limits to prevent malformed or malicious files from being parsed. 3) Employ application-level sandboxing or containerization for software components using libbiosig to limit the impact of potential code execution exploits. 4) Monitor network and system logs for anomalous activities related to MFER file handling, including unexpected crashes or memory errors. 5) Restrict access to systems processing biosignal data to trusted users and networks, and enforce least privilege principles. 6) Coordinate with medical device vendors and software providers to ensure timely updates and vulnerability disclosures. 7) Conduct security awareness training for staff handling biosignal data to recognize suspicious files and report incidents promptly. These measures, combined with rapid patch deployment, will reduce the risk of exploitation and protect sensitive medical data and systems.