# What changed in h2

> 1 change in h2 4 from its official release notes, upgrade guides and advisories: 1 security. Each one cited. Sources checked 2026-10-27. HTML: https://unstale.sh/pypi/h2/

To see which of these apply to a repository, run `npx @unstale/cli init` in it.

## h2 4

### Security

- h2: Duplicate Host header could facilitate request smuggling (4.4.1) — [security advisory](https://github.com/advisories/GHSA-6HR6-W5QG-QMWG)