Tinygsm

How buffer overflow happens in C TinyGSM sprintf and how to fix it

A critical buffer overflow vulnerability was discovered in `TinyGsmClientSequansMonarch.h` at line 515, where `sprintf` was writing a two-character hex string into a buffer only two bytes large — leaving no room for the null terminator. The fix replaces `sprintf` with `snprintf` and increases the buffer to three bytes, preventing a one-byte overflow that could corrupt adjacent memory in embedded firmware.