This vulnerability arises from improper bounds checking in the SOHM list-index deserialization code of HDF5 versions through 2.1.1. Specifically, if a crafted HDF5 file declares a num_messages count that exceeds the list_max, it triggers out-of-bounds heap reads and writes within the functions H5SM__cache_list_deserialize and H5SM__cache_list_verify_chksum. This can cause a denial of service by crashing the application processing the file. The CVSS 4.0 base score is 5.5, indicating medium severity. There is no vendor advisory or patch information available at this time.

An attacker can cause a denial of service by supplying a malicious HDF5 file that triggers out-of-bounds heap memory access during deserialization. This results in application crashes. There is no evidence of privilege escalation or code execution from the provided data.

Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Until a fix is available, avoid processing untrusted or unauthenticated HDF5 files to mitigate risk.