The AsyncHttpClient (AHC) library allows Java applications to easily execute HTTP requests and asynchronously process HTTP responses. From 2.1.0 until 3.0.14, the default ThreadSafeCookieStore does not retain whether a Set-Cookie response used a secure transport. It accepts Secure cookies received over plaintext and permits insecure cookies to overlay or delete existing Secure cookies with matching scope. An attacker controlling a plaintext same-site response can consequently plant, replace, or remove cookie state later sent to an HTTPS origin, enabling session fixation, CSRF-token replacement, or loss of security-relevant state. This issue is fixed in version 3.0.14.