A heap-use-after-free vulnerability exists in H5T__conv_f_f() in src/H5Tconv.c in HDF5 before 2.3.0. When converting a compound datatype containing floating-point members during a dataset read, a temporary buffer allocated with calloc() is freed and subsequently read from within the same conversion routine. An attacker who can supply a crafted HDF5 file containing a specially constructed compound datatype can trigger the use-after-free when the file is parsed by an application that reads the affected dataset, such as h5dump. This can result in a crash and, depending on heap layout and allocator behavior, may be exploitable for further memory corruption up to remote code execution.