structured-zstd decodes untrusted input, so a crash, hang, out-of-bounds access or unbounded allocation on any input is a security issue.
Report it privately through GitHub private vulnerability reporting, not in a public issue. Include the input that triggers it (or how to build it), the version or commit, the features enabled, and what you observed.
You will get an answer within a few days. A confirmed issue is fixed in a new release, and the advisory is published with credit to you unless you prefer otherwise.
Fixes go into the latest release only.