API Key Exposure Vulnerability in A2A Java SDK from A2A Project

CVE-2026-111763

What is CVE-2026-111763?

The A2A Java SDK, utilized for the Agent2Agent (A2A) Protocol, is susceptible to an API key exposure vulnerability. This flaw allows an attacker controlling a malicious remote agent to manipulate the default JDK-based client, causing it to inadvertently forward configured API keys to unauthorized third-party servers. This occurs when credentials are set via CredentialService; the AuthInterceptor directly uses the API key from the AgentCard as an HTTP header name, neglecting any verification that the key's location is appropriate. Moreover, the use of followRedirects(NORMAL) in the JdkA2AHttpClient can exacerbate the issue by permitting a cross-origin redirect under the agent's control, which can then forward these sensitive headers even when the standard Authorization header is removed. To mitigate this vulnerability, users are encouraged to update to version 1.3.0.Final, where the issue has been addressed.

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