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

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 (CVE-2025-61730).

See advisory page for additional details.

Inspect the project’s dependency declarations and lockfile for rustls, then review how the current 0.23.40 dependency is used. Confirm the project can move to patched version 0.23.45 or later, and run the existing test suite to verify that the dependency update does not break builds or TLS behavior.