The AsyncHttpClient (AHC) library allows Java applications to easily execute HTTP requests and asynchronously process HTTP responses. Prior to 3.0.13 and 2.16.1, cross-host request replay updates the current request but leaves the target request and related proxy context pointing at the original origin. Connection-pool selection, CONNECT handling, realm selection, and TLS setup can consequently send the original host's path, Host header, Authorization credentials, or plaintext request to the replay destination. Documented ResponseFilter failover and retry paths can trigger the replay. This issue is fixed in versions 3.0.13 and 2.16.1.

Affected: Maven: org.asynchttpclient:async-http-client

### Impact When a request is replayed onto a different host, the client updates only the current request and leaves the target request pointing at the original host. Four consumers read that stale value, and each one sends the first host's request, credentials, or both to the second host.

A replay happens through documented, ordinary features: a `ResponseFilter` that returns a different request, which is the supported failover pattern, and the IOException retry path. The attacker does not need to induce the replay; an application that uses failover produces it by design.

* The socket to host B is filed in the connection pool under host A's key. A later request the application addresses to A is served over the connection to B, and A's `Authorization` header goes to B. * Over a CONNECT tunnel, the client tunnels to B and negotiates TLS with B correctly, then writes A's request into that tunnel. B receives A's path, A's `Host`, and A's `Authorization`. TLS does not protect against this, because the handshake really is with B, so no certificate mismatch occurs. * The replay reuses the original realm, so A's credentials are regenerated onto a replay request that carries no realm of its own. The cross-origin redirect path strips realms for exactly this reason; the replay path never did. * The stale value also decides whether TLS is used at all. When the original request was `http://` and the replay is `https://`, no SSL handler is installed and the replayed request, credentials…

Affected: Ubuntu:Pro:14.04:LTS: async-http-client, Ubuntu:16.04:LTS: async-http-client, Ubuntu:18.04:LTS: async-http-client, Ubuntu:Pro:20.04:LTS: async-http-client, Ubuntu:22.04:LTS: async-http-client, Ubuntu:24.04:LTS: async-http-client, Ubuntu:26.04:LTS: async-http-client

The AsyncHttpClient (AHC) library allows Java applications to easily execute HTTP requests and asynchronously process HTTP responses. Prior to 3.0.13 and 2.16.1, cross-host request replay updates the current request but leaves the target request and related proxy context pointing at the original origin. Connection-pool selection, CONNECT handling, realm selection, and TLS setup can consequently send the original host's path, Host header, Authorization credentials, or plaintext request to the replay destination. Documented ResponseFilter failover and retry paths can trigger the replay. This issue is fixed in versions 3.0.13 and 2.16.1.