# CVE-2025-54489: biosig: A stack-based buffer overflow vulnerability exists in the MFER parsing functionality of The Biosig Project libbiosig...

CVE-2025-54489 is fixed in biosig on 1 platform by DEBIAN-CVE-2025-54489 (version 3.9.5-1), released August 25, 2025. It is not reported as exploited. Patch Radar priority: Urgent.

- Web page: https://patchblox.com/security/cve/CVE-2025-54489
- Priority: Urgent
- CVSS: 9.8 (critical)
- EPSS: 0.0071
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Aug 25, 2025

## Description

A stack-based buffer overflow vulnerability exists in the MFER parsing functionality of The Biosig Project libbiosig 3.9.0 and Master Branch (35a819fa). A specially crafted MFER file can lead to arbitrary code execution. An attacker can provide a malicious file to trigger this vulnerability.This vulnerability manifests on line 8970 of biosig.c on the current master branch (35a819fa), when the Tag is 63:                    else if (tag==63) {                      uint8_t tag2=255, len2=255;                        count = 0;                      while ((count<len) && !(FlagInfiniteLength && len2==0 && tag2==0)){                          curPos += ifread(&tag2,1,1,hdr);                          curPos += ifread(&len2,1,1,hdr);                          if (VERBOSE_LEVEL==9)                              fprintf(stdout,"MFER: tag=%3i chan=%2i len=%-4i tag2=%3i len2=%3i curPos=%i %li count=%4i\n",tag,chan,len,tag2,len2,curPos,iftell(hdr),(int)count);                            if (FlagInfiniteLength && len2==0 && tag2==0) break;                            count  += (2+len2);                          curPos += ifread(&buf,1,len2,hdr);    Here, the number of bytes read is not the Data Length decoded from the current frame in the file (`len`) but rather is a new length contained in a single octet read from the same input file (`len2`). Despite this, a stack-based buffer overflow condition can still occur, as the destination buffer is still `buf`, which has a size of only 128 bytes, while `len2` can be as large as 255.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | biosig Debian 14 | 3.9.5-1 | [DEBIAN-CVE-2025-54489](https://patchblox.com/security/data/fix/linux/debian-cve-2025-54489.md) | Aug 25, 2025 |

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