The vulnerability in HDF5 versions up to 2.3.0 involves the functions H5Z__nbit_decompress_one_byte, H5Z__nbit_decompress_one_nooptype, and H5Z__nbit_decompress_one_atomic in H5Znbit.c. These functions advance a read index into the compressed chunk buffer without proper bounds checking, allowing an out-of-bounds heap read. An attacker can craft an HDF5 file with N-Bit filter parameters that specify more decompressed data than the compressed chunk contains. When such a file is processed via H5Dread (e.g., by tools like h5ls or h5repack), this can cause disclosure of adjacent heap memory into decompressed dataset values.

An attacker can cause an out-of-bounds heap read leading to potential disclosure of adjacent heap memory contents. This could expose sensitive data present in memory during decompression of maliciously crafted HDF5 files. The vulnerability requires local access to trigger and user interaction to process the crafted file. There is no indication of remote exploitation or code execution.

Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Until a patch is available, avoid processing untrusted HDF5 files with affected versions of the library. Monitor vendor communications for updates and apply official fixes once released.