## rustls: An unauthenticated ServerHello poisons the per-name key-exchange record, so later ClientHellos carry only a classical X25519 share

- 種別: advisory
- 重大度: low
- 関連技術: rust
- 公開日時: 2026-10-27T16:08:54.000Z
- 情報源: GitHub Advisory Database (https://github.com/advisories/GHSA-w44r-93j7-qv28)
- パーマリンク: https://vulnpulse.app/items/ghsa-ghsa-w44r-93j7-qv28

影響: rust:rustls < 0.23.46 → 0.23.46, rust:rustls >= 0.24.0-dev.1, < 0.24.0-dev.2 → 0.24.0-dev.2
The client records the server-selected key-exchange group per server name when it processes the ServerHello, before the server is authenticated. A network attacker can answer one connection attempt for a target name with a ServerHello that selects X25519 and close the connection. Later ClientHellos for that name carry one X25519 share while supported_groups still lists X25519MLKEM768 first. If the server accepts that share instead of sending a HelloRetryRequest, the handshake completes with cla…