CVE-2026-85720: AsyncHttpClient: Origin credentials sent to the proxy on the plaintext CONNECT request
The AsyncHttpClient (AHC) library allows Java applications to easily execute HTTP requests and asynchronously process HTTP responses. From 2.0.0 until 2.16.1 and 3.0.12, a request using an HTTP proxy to reach an HTTPS origin can expose preemptive origin credentials because NettyRequestFactory and NettyRequestSender.sendRequestWithNewChannel attach Authorization to the plaintext CONNECT request before the TLS tunnel exists. Basic or Digest credentials and per-connection NTLM, Kerberos, or SPNEGO tokens intended for the origin are therefore visible to the proxy and to observers on the client-to-proxy hop. The tunneled request still receives origin Authorization after the tunnel is established, while Proxy-Authorization remains on CONNECT for its intended proxy recipient. This issue is fixed in versions 2.16.1 and 3.0.12.
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade to a fixed release to a version that resolves this vulnerability.
Fixed in 2.16.1 - Upgrade
Upgrade to a fixed release to a version that resolves this vulnerability.
Fixed in 3.0.12
Event History
Frequently Asked Questions
Which deployments are exposed to credential disclosure?
Java applications using AsyncHttpClient versions from 2.0.0 until 2.16.1 or 3.0.12 are exposed when they use an HTTP proxy to access an HTTPS origin and send preemptive origin credentials.
What credentials can be disclosed, and who can see them?
Basic or Digest origin credentials, plus per-connection NTLM, Kerberos, or SPNEGO tokens, can be attached to the plaintext CONNECT request. They are visible to the HTTP proxy and to observers on the client-to-proxy network hop.
Does proxy authentication cause the issue?
No. Proxy-Authorization remains on CONNECT for the proxy as intended; the issue is that origin Authorization is also sent before the TLS tunnel is established.
What is the immediate remediation?
Upgrade AsyncHttpClient to version 2.16.1 or 3.0.12. If upgrading cannot happen immediately, avoid using an HTTP proxy for HTTPS requests that use preemptive origin credentials.