RUSTSEC-2026-0285: TLS 1.3 handshake messages incorrectly accepted across encryption level boundaries

> TLS 1.3 handshake messages incorrectly accepted across encryption level boundaries

| Details | |
| ------------------- | ---------------------------------------------- |
| Package | `rustls` |
| Version | `0.23.43` |
| URL | [https://github.com/rustls/rustls/security/advisories/GHSA-2mjx-qc3c-rqvc](https://github.com/rustls/rustls/security/advisories/GHSA-2mjx-qc3c-rqvc) |
| Date | 2026-09-14 |
| Patched versions | `>=0.23.45` |
| Unaffected versions | `<0.23.13` |

Rustls accepted TLS 1.3 handshake messages sent at the wrong encryption level
when they followed a key-changing message in the same record. For example,
a plaintext `EncryptedExtensions` message packed into the same record as the
`ServerHello` was accepted.

RFC 8446 section 5.1 requires that handshake messages do not span key changes,
and that implementations terminate the connection with an "unexpected_message"
alert if they do.

The handshake transcript is still authenticated, so a network-position attacker
cannot use this to alter or complete a handshake; the practical effect is that
a peer could send handshake messages that should be encrypted in plaintext
without rustls rejecting the connection.

This is functionally the same bug as Go's
[GO-2026-4340](https://pkg.go.dev/vuln/GO-2026-4340) (CVE-2025-61730).

See [advisory page](https://rustsec.org/advisories/RUSTSEC-2026-0285.html) for additional details.

Start with the linked RustSec advisory and the rustls package details, then inspect this project's dependency metadata to determine whether rustls 0.23.43 is used. Done means the vulnerable version is no longer selected and the project’s existing checks pass; the issue does not name a source file or test to run.

Written by the indexing model from the issue text.