TLS Handshake Encryption Level Bypass in Rustls by Rust Foundation

CVE-2026-123613

What is CVE-2026-123613?

Rustls versions prior to 0.23.45 are susceptible to a TLS 1.3 handshake issue where encrypted extensions in a server hello can be accepted unencrypted due to improper record-boundary alignment. This vulnerability allows attackers, either through a compromised peer or via an on-path attack, to exploit the handling of key-changing messages in the same record, leading to potential information exposure.

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