CVE-2026-19028 HDF5 integer underflow in Fletcher32 filter leads to massive out-of-bounds read

H5Zfilterfletcher32 in H5Zfletcher32.c in HDF5 through 2.3.0 computes the data length to checksum by subtracting the 4-byte trailing checksum size from the input buffer size without checking that the buffer is at least 4 bytes, allowing a sizet underflow. This allows attackers to cause a denial o...