CVE-2025-66044 is a stack-based buffer overflow vulnerability identified in The Biosig Project's libbiosig version 3.9.1, specifically within the MFER (Multi-File EEG Record) parsing functionality. The vulnerability arises when processing MFER files containing a Tag value of 64, which triggers improper handling of input data leading to a buffer overflow on the stack. This overflow can overwrite critical control data such as return addresses, enabling an attacker to execute arbitrary code with the privileges of the application using libbiosig. The flaw requires no privileges or user interaction, and can be exploited remotely by providing a maliciously crafted MFER file to the vulnerable system. The vulnerability is classified under CWE-121 (Stack-based Buffer Overflow), a common and dangerous software weakness. The CVSS v3.1 base score of 9.8 indicates critical severity with network attack vector, low attack complexity, no privileges required, and no user interaction needed. The impact encompasses full compromise of confidentiality, integrity, and availability of affected systems. While no public exploits have been reported yet, the nature of the vulnerability makes it a prime target for attackers once weaponized. Libbiosig is used in biomedical signal processing applications, including EEG data analysis, which are prevalent in research, healthcare, and biometric authentication systems. The lack of available patches at the time of publication increases the urgency for mitigation and monitoring.

For European organizations, the impact of CVE-2025-66044 is significant, especially those involved in biomedical research, healthcare, and biometric systems that rely on libbiosig for signal processing. Exploitation could lead to full system compromise, data theft, manipulation of sensitive biomedical data, disruption of critical healthcare services, and potential breaches of patient privacy under GDPR regulations. The arbitrary code execution capability could allow attackers to deploy ransomware, steal intellectual property, or pivot within networks to access other critical infrastructure. Given the critical nature of healthcare and research sectors in Europe, such an attack could have cascading effects on public health and safety. Additionally, compromised biometric systems could undermine security controls in physical and logical access management. The absence of known exploits currently provides a window for proactive defense, but the high severity score demands immediate attention to prevent future attacks.

1. Immediate mitigation should focus on isolating systems that process MFER files using libbiosig 3.9.1 to prevent exposure to untrusted inputs. 2. Implement strict input validation and sanitization for all MFER files before processing, especially checking for Tag values and file integrity. 3. Employ sandboxing or containerization techniques to limit the impact of potential exploitation by isolating the parsing process. 4. Monitor network and system logs for unusual activity related to MFER file handling or unexpected crashes indicative of exploitation attempts. 5. Coordinate with The Biosig Project and relevant vendors for timely patches or updates addressing this vulnerability. 6. Consider deploying intrusion detection/prevention systems (IDS/IPS) with signatures targeting malformed MFER files or buffer overflow patterns. 7. Conduct security awareness training for staff handling biomedical data to recognize suspicious files and report anomalies. 8. Review and strengthen endpoint security controls to detect and block arbitrary code execution attempts. 9. Maintain up-to-date backups of critical biomedical data to enable recovery in case of compromise. 10. Engage in threat intelligence sharing with European cybersecurity communities to stay informed about emerging exploits.