A2A Project A2A Java SDK up to 1.2.x AuthInterceptor AuthInterceptor.java AuthInterceptor.intercept cross-domain policy

Summaryinfo

A vulnerability marked as problematic has been reported in A2A Project A2A Java SDK up to 1.2.x. Affected is the function AuthInterceptor.intercept of the file client/transport/spi/src/main/java/org/a2aproject/sdk/client/transport/spi/interceptors/auth/AuthInterceptor.java of the component AuthInterceptor. This manipulation causes cross-domain policy. The identification of this vulnerability is CVE-2026-111763. It is possible to initiate the attack remotely. There is no exploit available. It is suggested to upgrade the affected component.

Detailsinfo

A vulnerability classified as problematic was found in A2A Project A2A Java SDK up to 1.2.x. Affected by this vulnerability is the function AuthInterceptor.intercept of the file client/transport/spi/src/main/java/org/a2aproject/sdk/client/transport/spi/interceptors/auth/AuthInterceptor.java of the component AuthInterceptor. The manipulation with an unknown input leads to a cross-domain policy vulnerability. The CWE definition for the vulnerability is CWE-942. The product uses a cross-domain policy file that includes domains that should not be trusted. As an impact it is known to affect confidentiality. The summary by CVE is:

A2A Java SDK is the official Java SDK for the Agent2Agent (A2A) Protocol. Prior to 1.3.0.Final, a malicious or compromised remote agent can cause the default JDK-based client to forward a configured API key to a third-party server. When a client application configures credentials through `CredentialService`, `AuthInterceptor.intercept` in `client/transport/spi/src/main/java/org/a2aproject/sdk/client/transport/spi/interceptors/auth/AuthInterceptor.java` uses `APIKeySecurityScheme.name()` from the remote AgentCard directly as the HTTP header name containing the credential, without checking that the declared location is HEADER. JdkA2AHttpClient uses followRedirects(NORMAL), so an agent-controlled cross-origin redirect forwards the custom credential-bearing header even when the standard Authorization header is stripped. The attack requires configured API key credentials for the agent's security scheme and control of the agent's AgentCard and redirect response, but no additional client privileges. This issue is fixed in version 1.3.0.Final.

It is possible to read the advisory at github.com. This vulnerability is known as CVE-2026-111763 since 10/16/2026. The exploitation appears to be difficult. The attack can be launched remotely. The exploitation doesn't need any form of authentication. It demands that the victim is doing some kind of user interaction. Technical details of the vulnerability are known, but there is no available exploit.

Upgrading to version 1.3.0.Final eliminates this vulnerability.

The vulnerability is also documented in the vulnerability database at EUVD (EUVD-2026-105127). Be aware that VulDB is the high quality source for vulnerability data.

Productinfo

Type

• Project Management Software

Vendor

• A2A Project

Name

• A2A Java SDK

Version

• 1.0
• 1.1
• 1.2

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Be aware that VulDB is the high quality source for vulnerability data.

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