CVE-2025-54494 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 resides in the MFER file parsing functionality, where improper handling of a specific tag value (tag 133, or 0x85) in biosig.c leads to an unchecked buffer operation. At line 9205, the code increments a buffer position pointer by reading data from a file without adequate bounds checking, allowing a specially crafted MFER file to overflow the stack buffer. This overflow can corrupt the stack, enabling an attacker to execute arbitrary code remotely without requiring any privileges or user interaction. The vulnerability is classified under CWE-121 (Stack-based Buffer Overflow) and has a CVSS v3.1 base score of 9.8, indicating critical severity with network attack vector, low attack complexity, no privileges required, and no user interaction needed. Exploitation could lead to full system compromise, including confidentiality, integrity, and availability impacts. Although no known exploits are currently reported in the wild, the nature of the vulnerability and its critical score suggest that exploitation is feasible and potentially highly damaging. The Biosig Project's libbiosig is a library used for biosignal processing, including EEG and other physiological data formats, and is integrated into various research and medical software tools that handle MFER files. The vulnerability's root cause is a lack of proper input validation and bounds checking during MFER tag parsing, which is a common and severe programming error in C-based libraries handling untrusted input data.

For European organizations, especially those involved in healthcare, biomedical research, and medical device manufacturing or usage, this vulnerability poses a significant risk. Many European hospitals, research institutions, and medical device vendors utilize biosignal processing software that may depend on libbiosig for handling MFER files. Successful exploitation could allow attackers to execute arbitrary code on systems processing these files, potentially leading to data breaches involving sensitive patient information, disruption of critical medical research, or compromise of medical devices. Given the criticality and ease of exploitation, attackers could leverage this vulnerability to gain persistent access, disrupt healthcare operations, or manipulate biosignal data integrity. This could undermine patient safety, violate GDPR data protection regulations, and cause reputational and financial damage. The lack of authentication and user interaction requirements further increases the threat surface, as attackers can deliver malicious MFER files via network vectors such as email attachments, file uploads, or network shares. The vulnerability also threatens the availability of systems processing biosignal data, which may be critical in clinical environments.

European organizations should immediately audit their software stacks to identify any usage of libbiosig versions 3.9.0 or the affected master branch. Since no official patches are currently linked, organizations should consider the following mitigations: 1) Temporarily disable or restrict processing of MFER files from untrusted sources until a patched version is available. 2) Implement strict input validation and sandboxing around any component that parses MFER files to contain potential exploitation attempts. 3) Employ application-layer firewalls or intrusion prevention systems to detect and block malformed MFER files. 4) Monitor network and endpoint logs for unusual activity related to biosignal processing applications. 5) Engage with The Biosig Project or community to obtain or contribute patches addressing the buffer overflow. 6) For developers using libbiosig, review and harden the parsing code by adding bounds checks and safe memory handling practices. 7) Educate staff about the risks of opening or processing untrusted biosignal files. These steps go beyond generic advice by focusing on the specific file format and library involved, emphasizing containment, detection, and proactive code review.