CVE-2026-107281 in Async-Http-Client
Summary
by MITRE • 10/08/2026
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, the HTTP/1.1 connection-pool key excludes the authenticated principal for connection-oriented NTLM and Negotiate authentication. A pooled socket authenticated for one request can be reused by a request carrying another principal, and the server executes that later request as the first identity. Basic and Digest are not affected because they authenticate each request. This issue is fixed in versions 3.0.13 and 2.16.1.
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Analysis
by VulDB Data Team • 10/08/2026
The AsyncHttpClient library serves as a critical component for Java-based applications requiring efficient, non-blocking HTTP communication by executing requests asynchronously and processing responses without blocking the calling thread. A significant security flaw was identified in versions prior to 3.0.13 and 2.16.1 regarding how connection pools manage authenticated sessions under specific authentication schemes. Specifically, when utilizing connection-oriented NTLM or Negotiate authentication protocols, the library failed to include the authenticated principal within the key used for identifying pooled connections. This architectural oversight means that the pool treats sockets as interchangeable based solely on network parameters such as host and port, ignoring the identity of the user associated with the session.
In a typical operational scenario involving NTLM or Negotiate authentication, a client establishes a connection to an HTTP server after successfully authenticating with specific credentials. Due to the vulnerability, if another request is initiated using different credentials but targeting the same server endpoint, the AsyncHttpClient may incorrectly reuse the existing pooled socket that was authenticated for the first user. Consequently, the second request is transmitted over the established channel without re-authentication, causing the remote server to process this subsequent request under the identity of the original principal who owns the connection. This behavior fundamentally breaks the principle of least privilege and session isolation expected in secure web communications.
The impact of this vulnerability is severe, as it enables potential authorization bypass attacks where an attacker or a compromised component with lower privileges can leverage the authenticated channel of a higher-privilege user to perform actions on their behalf. Since Basic and Digest authentication schemes are not affected by this specific flaw due to their stateless nature which requires re-authentication for each request, the risk is isolated strictly to connection-oriented protocols that maintain session state over persistent connections. This discrepancy highlights a critical gap in how identity context is managed within pooled network resources, potentially leading to unauthorized data access or modification depending on the privileges of the impersonated user.
To mitigate this vulnerability, organizations must ensure that all instances of AsyncHttpClient are upgraded to version 3.0.13 or later for the major branch and 2.16.1 or later for the legacy branch. These updates correct the connection-pooling logic by incorporating the authenticated principal into the pool key, thereby ensuring that sockets are strictly bound to their respective identities and cannot be shared across different users. From a broader security architecture perspective, this issue aligns with CWE-280, which describes improper handling of validation for authorization-related functions, as well as ATT&CK technique T1550, specifically sub-technique T1550.004 involving the use of legitimate application protocols like HTTP to bypass defenses through session hijacking or impersonation within trusted connections.