Mdbx

How buffer overflow in fgets() happens in C and how to fix it

A critical buffer overflow vulnerability was discovered in the `readline()` function of `mdbx_load.c`, where an `fgets()` call passed a size parameter exceeding the actual allocated buffer by one byte. This off-by-one error could allow an attacker to trigger heap corruption by supplying oversized input via stdin, potentially leading to arbitrary code execution. The fix corrects the size parameter from `buf->iov_len + 1` to `buf->iov_len`, ensuring reads never exceed buffer boundaries.