iOS Buffer Overflow (CVE-2026-20777)

Vendor-confirmed - CVE-2026-20777 is a high-severity buffer overflow in Biosig Project’s libbiosig 3.9.2 that allows an attacker to execute arbitrary code by supplying a specially crafted .wft file. Organizations should prioritize patching once the official fix is released and avoid processing untrusted .wft files in the interim.

Overview

A critical memory corruption vulnerability has been identified in The Biosig Project’s libbiosig, a software library used to read and process various biomedical signal file formats. The flaw resides in the code that handles Nicolet WFT files. By creating a specially crafted malicious .wft file, an attacker could trigger a heap buffer overflow.

Vulnerability Details

In simple terms, the library does not properly validate the size of data being written into a reserved area of a computer’s memory (the heap) when parsing a WFT file. This allows an attacker to overflow the allocated buffer with their own data. If successfully exploited, this overflow can corrupt adjacent memory structures and, in the worst case, allow the attacker to execute arbitrary code on the system. The vulnerability is present in libbiosig version 3.9.2 and the development master branch at commit db9a9a63.

Impact

The primary risk is arbitrary code execution with the privileges of the application using the vulnerable libbiosig library. This could lead to:

• Complete compromise of the host system running the affected software.
• Installation of malware, ransomware, or backdoors.
• Theft or manipulation of sensitive biomedical data being processed.
• Disruption of healthcare or research workflows that depend on this library.

Given the high CVSS score of 8.1, this vulnerability poses a significant security risk, especially in environments where libbiosig is used to process files from untrusted sources.

Remediation and Mitigation

Immediate Action Required:

1. Patch or Update: The most effective solution is to apply the official patch once it is released by The Biosig Project maintainers. Monitor the official project repository for updates. All users should upgrade to a patched version as soon as it becomes available.

2. Immediate Mitigation (Workaround): Until a patch is deployed, implement strict input validation. Do not process Nicolet .wft files from untrusted or unknown sources with applications linked to the vulnerable versions of libbiosig. If file processing is essential, consider using isolated, sandboxed environments with minimal privileges to limit potential damage from exploitation.

3. Inventory and Assess: Identify all applications, research tools, or medical devices in your environment that incorporate libbiosig for biomedical signal analysis. Contact the vendors of those downstream products to inquire about their update plans.

Note: Simply scanning for malicious files is not a reliable mitigation, as the flaw is in the parsing logic itself. Updating the library is the only definitive fix.