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 9090 of biosig.c on the current master branch (35a819fa), when the Tag is 64: else if (tag==64) //0x40 { // preamble char tmp[256]; // [1] curPos += ifread(tmp,1,len,hdr); In this case, the overflowed buffer is the newly-declared `tmp` \[1\] instead of `buf`. While `tmp` is larger than `buf`, having a size of 256 bytes, a stack overflow can still occur in cases where `len` is encoded using multiple octets and is greater than 256.