{"id":"RUSTSEC-2025-0004","summary":"ssl::select_next_proto use after free","details":"In `openssl` versions before `0.10.70`, `ssl::select_next_proto` can return a slice pointing into the `server` argument's buffer but with a lifetime bound to the `client` argument. In situations where the `server` buffer's lifetime is shorter than the `client` buffer's, this can cause a use after free. This could cause the server to crash or to return arbitrary memory contents to the client.\n\n`openssl` 0.10.70 fixes the signature of `ssl::select_next_proto` to properly constrain the output buffer's lifetime to that of both input buffers.\n\nIn standard usage of `ssl::select_next_proto` in the callback passed to `SslContextBuilder::set_alpn_select_callback`, code is only affected if the `server` buffer is constructed *within* the callback. For example:\n\nNot vulnerable - the server buffer has a `'static` lifetime:\n```rust\nbuilder.set_alpn_select_callback(|_, client_protos| {\n    ssl::select_next_proto(b\"\\x02h2\", client_protos).ok_or_else(AlpnError::NOACK)\n});\n```\n\nNot vulnerable - the server buffer outlives the handshake:\n```rust\nlet server_protos = b\"\\x02h2\".to_vec();\nbuilder.set_alpn_select_callback(|_, client_protos| {\n    ssl::select_next_proto(&server_protos, client_protos).ok_or_else(AlpnError::NOACK)\n});\n```\n\nVulnerable - the server buffer is freed when the callback returns:\n```rust\nbuilder.set_alpn_select_callback(|_, client_protos| {\n    let server_protos = b\"\\x02h2\".to_vec();\n    ssl::select_next_proto(&server_protos, client_protos).ok_or_else(AlpnError::NOACK)\n});\n```","aliases":["CVE-2025-24898","GHSA-rpmj-rpgj-qmpm"],"modified":"2025-10-28T06:02:18Z","published":"2025-02-02T12:00:00Z","database_specific":{"license":"CC0-1.0"},"references":[{"type":"PACKAGE","url":"https://crates.io/crates/openssl"},{"type":"ADVISORY","url":"https://rustsec.org/advisories/RUSTSEC-2025-0004.html"},{"type":"ADVISORY","url":"https://github.com/sfackler/rust-openssl/security/advisories/GHSA-rpmj-rpgj-qmpm"},{"type":"WEB","url":"https://github.com/sfackler/rust-openssl/pull/2360"}],"affected":[{"package":{"name":"openssl","ecosystem":"crates.io","purl":"pkg:cargo/openssl"},"ranges":[{"type":"SEMVER","events":[{"introduced":"0.0.0-0"},{"fixed":"0.10.70"}]}],"ecosystem_specific":{"affects":{"functions":["openssl::ssl::select_next_proto"],"os":[],"arch":[]},"affected_functions":null},"database_specific":{"source":"https://github.com/rustsec/advisory-db/blob/osv/crates/RUSTSEC-2025-0004.json","informational":null,"cvss":null,"categories":["memory-exposure"]}}],"schema_version":"1.7.3"}