Rustls 0.23.45 Released To Fix Two Year Old Security Issue

While the Rustls modern TLS library is written in the Rust programming language with a focus on memory safety, as we've seen out of other Rust project re-implementations in the past, the new implementations can lead to other security bugs of their own. Out today is Rustls 0.23.45 to fix a security issue introduced back in 2024 with Rustls while the likes of OpenSSL, BoringSSL, and others are unaffected. Rustls 0.23.45 was released in order to fix a bug where TLS 1.3 handshake messages were incorrectly accepted across encryption level boundaries. The now-public advisory notes that this incorrect handling of TLS 1.3 handshake messages across encryption level boundaries could lead an on-path attacker to injecting plain text messages that are then accepted by Rustls. Ultimately it comes down to Rustls' implementation of TLS 1.3 having been out-of-spec compared to RFC 8446. Today's Rustls 0.23.45 announcement adds: "Rustls accepted TLS 1.3 handshake messages sent at the wrong encryption level when they followed a key-changing message in the same record. 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." The issue is similar to this Go vulnerability from January. The issue was fixed in the Rustls code yesterday and now available via v0.23.45. The issue has been present in Rustls since v0.23.13 released back in September 2024.