External risk intelligence

Libbiosig MFER Parsing Stack Buffer Overflow Leads to Code Execution.

CVE advisorySeverity: CRITICAL (CVSS 9.8)

CVE-2025-66047

libbiosig is a library used for processing biomedical signal data files (MFER). It is typically integrated into specialized, local, or offline research and analysis software rather than deployed as an internet-facing service. The requirement for a specially crafted file to be parsed by an application using this library makes public internet exposure and reachability for this specific vulnerability very unlikely.

Out-of-bounds Write

Libbiosig Project Libbiosig

before 3.9.2

Halo Surface Signal: 1 out of 5 — much less likely to be public-facing.

External exposure likelihood

Horizon Alert

Summary of the vulnerability and why it matters

The Biosig Project's libbiosig library contains critical vulnerabilities in its MFER file parsing, potentially allowing remote code execution if a user opens a specially crafted file. This issue matters because it could enable unauthorized control of systems processing biomedical signal data. The main concern is confirming relevance and exposure.

Flaws allow malicious files to run code.
Critical for systems processing biomedical data.
Confirm if your systems use this software.

Attack Path

How an attacker could exploit the issue

An attacker could achieve arbitrary code execution by tricking a user into opening a specially crafted MFER file. This malicious file, when parsed by the vulnerable library, exploits a buffer overflow flaw related to a specific tag value, allowing the attacker to gain control of the program's execution.

Requires user interaction to open a crafted file.
Triggered when parsing a malicious MFER file.
Leads to arbitrary code execution.

Live Threat

Current exploitation, exposure, and threat context

This vulnerability could allow an attacker to execute arbitrary code by providing a specially crafted MFER file to an application that uses the libbiosig library, potentially affecting the integrity and availability of the system.

System integrity and data.
Malicious MFER file parsing.
Arbitrary code execution.

Operational Fix

Recommended remediation, mitigation, and detection steps

The Biosig Project's libbiosig library, used for parsing MFER files, contains stack-based buffer overflow vulnerabilities. Given its typical integration into specialized research or analysis software rather than internet-facing services, immediate action will likely involve identifying systems that process MFER files, assessing their criticality, and coordinating with application owners or development teams for remediation during planned maintenance.

Application owners should prioritize triage.
Verify MFER file processing systems.
Plan remediation based on risk.

Supplementary metadata

CVSS vector

Validate whether this threat affects your internet-facing exposure.

Halo Threat Intelligence helps prioritize remediation with Halo Surface Signal and H/A/L/O context. Start exposure validation with a free external attack surface trial.

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Frequently asked questions

What is libbiosig?

libbiosig is a software library developed by The Biosig Project. It is primarily used by researchers and engineers to read, process, and analyze biomedical signal data, particularly files formatted as MFER (Medical Data Information Format).

What does CWE-121 and CWE-787 mean for CVE-2025-66047?

These codes identify stack-based buffer overflows. In simple terms, the software fails to properly check the size of incoming data when parsing an MFER file. Because the data exceeds the memory space reserved for it, the extra information can overwrite critical parts of the program's memory, potentially allowing an attacker to hijack the computer's execution.

How is this vulnerability triggered?

The flaw is triggered when an application using an older version of libbiosig attempts to parse a specially crafted MFER file. It is not triggered by simply having the library installed; the vulnerability requires the library to actively process a malicious file that contains specific data patterns, such as the problematic 'Tag 131'.

Do I need to worry about this if my system is internal?

While the CVSS score reflects a network attack vector, Halo Surface Signal notes that libbiosig is typically used in specialized, local, or offline research environments. Because it is rarely used as an internet-facing service, public reachability is very unlikely. However, internal systems processing untrusted or externally sourced data files should still be considered.

When should I prioritize fixing this library?

Prioritize your response by identifying which of your applications actively process MFER files. Since this is a library, you cannot patch it in isolation; you must coordinate with your development teams or software vendors to update the specific applications that include the vulnerable libbiosig code.

References

talosintelligence.com/vulnerability_reports/TALOS-2025-2296

Written by Nicholas Merritt

Nicholas Merritt is VP of Security Solutions at Halo Security. With more than 25 years across application security, vulnerability prioritization, and offensive security, he helps teams translate threat data into practical exposure validation and remediation focus. He authors Halo Threat Intelligence CVE advisories using Halo Surface Signal and H/A/L/O context to prioritize internet-facing risk.