CVE-2025-53557 is a critical heap-based buffer overflow vulnerability identified in the MFER parsing functionality of The Biosig Project's libbiosig library, specifically affecting versions 3.9.0 and the Master Branch (commit 35a819fa). Libbiosig is an open-source library used for biosignal processing, including formats like EEG, ECG, and other physiological data. The vulnerability arises when the library processes specially crafted MFER files, which are a format for encoding biosignal data. Due to improper bounds checking during parsing, an attacker can cause a heap-based buffer overflow, potentially leading to arbitrary code execution. This means that by supplying a maliciously crafted MFER file to an application or system using the vulnerable libbiosig versions, an attacker can execute arbitrary code with the privileges of the affected process. The CVSS v3.1 score is 9.8 (critical), reflecting that the vulnerability is remotely exploitable (network vector), requires no privileges or user interaction, and impacts confidentiality, integrity, and availability severely. No known exploits are currently reported in the wild, but the severity and ease of exploitation make this a high-risk issue. The lack of available patches at the time of publication increases the urgency for mitigation and monitoring. Given libbiosig’s use in medical and research environments, exploitation could compromise sensitive physiological data and disrupt critical biosignal processing workflows.

For European organizations, particularly those in healthcare, biomedical research, and medical device manufacturing, this vulnerability poses a significant risk. Many European hospitals and research institutions utilize biosignal processing tools that may incorporate libbiosig, either directly or as part of larger software suites. Exploitation could lead to unauthorized access to sensitive patient data, manipulation or corruption of biosignal data, and disruption of diagnostic or monitoring systems. This could result in privacy violations under GDPR, impact patient safety, and cause operational downtime. Additionally, compromised systems could be leveraged as footholds for further network intrusion. The critical nature of the vulnerability and the lack of required authentication or user interaction make it a prime target for attackers aiming to infiltrate healthcare environments, which are increasingly targeted by cybercriminals and state-sponsored actors. The potential for arbitrary code execution also raises concerns about ransomware or data exfiltration campaigns targeting European healthcare infrastructure.

European organizations should immediately identify any use of libbiosig 3.9.0 or the affected master branch in their software stacks, including third-party applications that may embed the library. Until an official patch is released, organizations should consider the following mitigations: 1) Implement strict input validation and sandboxing for any application processing MFER files to limit the impact of malicious inputs. 2) Employ network-level controls to restrict access to systems that process biosignal data, minimizing exposure to untrusted sources. 3) Monitor logs and network traffic for anomalous activity related to MFER file handling or unexpected process behavior. 4) Engage with software vendors to prioritize patch development and deployment. 5) Where feasible, isolate biosignal processing environments from critical networks to contain potential exploitation. 6) Conduct security awareness training for staff handling biosignal data to recognize suspicious files or activities. 7) Prepare incident response plans specifically addressing potential exploitation of biosignal processing vulnerabilities. These targeted actions go beyond generic advice by focusing on the unique context of biosignal processing and the specific attack vector.