CVE-2025-54489 is a stack-based buffer overflow vulnerability identified in The Biosig Project's libbiosig library, specifically in versions 3.9.0 and the master branch (commit 35a819fa). The vulnerability resides in the MFER file parsing code, particularly when processing tag 63. The parsing logic reads a length value (len2) from the input file, which can be as large as 255 bytes, but copies data into a fixed-size buffer of only 128 bytes (buf). This discrepancy allows an attacker to overflow the stack buffer by providing a specially crafted MFER file with maliciously large len2 values. The overflow can overwrite the stack, enabling arbitrary code execution. The vulnerability is exploitable remotely without authentication or user interaction, as it only requires the victim to process a malicious MFER file. The CVSS v3.1 score is 9.8 (critical), reflecting the vulnerability's ease of exploitation (network vector, low attack complexity), and its impact on confidentiality, integrity, and availability. The root cause is improper bounds checking during the parsing loop, where the code increments counters and reads data without verifying that len2 does not exceed the buffer size. No patches were listed at the time of disclosure, but remediation would involve fixing the input validation and buffer size checks. This vulnerability is particularly concerning for applications relying on libbiosig for biosignal data processing, such as medical devices, research tools, and clinical software.

The impact on European organizations is significant, especially those in healthcare, biomedical research, and clinical diagnostics that utilize The Biosig Project's libbiosig library for biosignal processing. Successful exploitation could lead to arbitrary code execution, allowing attackers to compromise system confidentiality by accessing sensitive patient data, integrity by altering biosignal data or analysis results, and availability by causing system crashes or denial of service. This could disrupt critical healthcare services, research activities, and patient monitoring systems. Additionally, compromised systems could be used as footholds for lateral movement within networks, increasing the risk of broader breaches. Given the criticality and ease of exploitation, organizations face a high risk of targeted attacks or automated exploitation attempts once proof-of-concept exploits become available. The lack of authentication and user interaction requirements further amplifies the threat, as malicious files could be delivered via network services or removable media without user awareness.

1. Monitor The Biosig Project's official channels for patches addressing CVE-2025-54489 and apply them promptly once released. 2. Until patches are available, implement strict input validation and sanitization on all MFER files before processing, including limiting the maximum allowed length fields to the buffer size or less. 3. Employ sandboxing or containerization techniques to isolate the libbiosig processing environment, minimizing potential damage from exploitation. 4. Use application-layer firewalls or intrusion detection systems to detect and block malformed or suspicious MFER files. 5. Conduct code audits and static analysis on any custom integrations of libbiosig to identify similar unsafe parsing patterns. 6. Educate staff on the risks of processing untrusted biosignal files and enforce policies restricting file sources. 7. Maintain up-to-date backups and incident response plans tailored to potential exploitation scenarios. 8. Consider deploying runtime protections such as stack canaries, address space layout randomization (ASLR), and control flow integrity (CFI) in applications using libbiosig to reduce exploitation success.