GHSA-vxxm-wwqh-mh47

### Impact

An issue in `DigestAuthProvider.verify`:

**Algorithm silently forced to MD5.** The configured `algorithm` parameter was ignored — every verification used MD5 regardless of configuration. Deployments believing they were running SHA-256 Digest auth were silently inheriting MD5's collision weaknesses, including documented attack paths against Digest schemes that rely on the hash being collision-resistant.

**Who is affected:** any application using `http4k-security-digest` for HTTP Digest authentication. The bug has been present since `DigestAuthProvider` was introduced (commit `8a52b615b1`, 2021).

### Patches

| Line | Fixed in | Edition | |------|----------|---------| | v6.x (Community) | **6.50.0.0** | Community | | v5.x (LTS) | **5.42.0.0** | Enterprise — contact [enterprise@http4k.org](mailto:enterprise@http4k.org) (if Digest auth is present in your v5.x line) | | v4.x (LTS) | **4.51.0.0** | Enterprise — contact [enterprise@http4k.org](mailto:enterprise@http4k.org) (if Digest auth is present in your v4.x line) |

The fix: - Hashes with the configured `algorithm` instead of hardcoded MD5.

### Workarounds

For deployments that cannot upgrade immediately: - **Algorithm gap:** do not rely on `algorithm` configuration; assume MD5 is in use and treat the Digest credentials as low-trust.

### References

- Vulnerability first present: [`8a52b615b1`](https://github.com/http4k/http4k/commit/8a52b615b1) - Algorithm fix: [`65d23d99fc`](https://github.com/http4k/http4k/commit/65d23d99fc) - Fix release: [v6.50.0.0](https://github.com/http4k/http4k/releases/tag/6.50.0.0) - Background: [RFC 7616 — HTTP Digest Access Authentication](https://datatracker.ietf.org/doc/html/rfc7616)