Rustls as the modern TLS library written in the Rust programming language with an emphasis on memory safety is out today with its v0.23.46 release in order to ship four new security fixes.

The first security fix in this new Rustls library release is the Brotli certificate decompression, which is built-in but disabled by default, can allocate an attacker-control amount of memory up to 1GB before authentication takes place.

Another issue is the session debug formatting exposes TLS master secrets and resumption PSKs. In turn these important keys can be disclosed via log files.

The third issue is an unauthenticated ServerHello poisons the per-name key-exchange hints whereby later ClientHellos carry only a classic X25519 share.

The final security issue fixed in this release is application data that a client buffers prior to the handshake completing is sent to the server even if the server rejects Encryptped Client Hello (ECH).

In addition to those four security fixes, there are also several other bug fixes pulled into Rustls 0.23.46. Thirteen of the bugs fixed in this release were discovered and reported by OpenAI, including two of the security issues.

Downloads and more details on the just-released Rustls 0.23.46 via GitHub.