A2A Java SDK is the official Java SDK for the Agent2Agent (A2A) Protocol. Prior to 1.3.0.Final, the default InMemoryTaskStore configuration performs no authorization on task reads: the no-argument constructor sets authorizationProvider to null, and InMemoryTaskStore.get(String taskId) returns the stored task without checking the caller or owner. Authorization depends on supplying a TaskAuthorizationProvider and routing requests through AuthorizationRequestHandlerDecorator, whether installed through CDI or explicitly by the application. Default store wiring and manually constructed DefaultRequestHandler.builder().build() handlers, including integrations such as Spring, leave task reads unprotected when no effective authorization-provider and decorator check is installed. In a multi-caller deployment using the default configuration, a caller who knows or guesses another caller's task ID can retrieve the task status, context ID, message history, and artifacts. The default/reference transport endpoints do not enforce authentication, so the task-read disclosure is reachable by an unauthenticated caller rather than requiring a privileged account. This issue is fixed in version 1.3.0.Final.

Affected: Maven: org.a2aproject.sdk:a2a-java-sdk-server-common

Draft text for GHSA-qw47-mcm5-934w. The body below drops into the GitHub advisory description field; the metadata block maps to the form fields. Set the patched version at release; publish when the fix ships._

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- **Ecosystem:** Maven - **Affected package:** `org.a2aproject.sdk:a2a-java-sdk-server-common` (task store / authorization) - **Affected versions:** `<= 1.2.0.Final` (and `1.2.1.Final-SNAPSHOT` on `main` prior to the fix) - **Patched version:** _(the release that carries the fix, e.g. 1.2.1.Final)_ - **CWE:** CWE-1188 (Insecure Default Initialization), CWE-862 (Missing Authorization) - **Severity:** High - **CVSS v3.1:** `CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N` (7.5, High)

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## Details

The default task store performs no authorization on task reads. `InMemoryTaskStore`'s no-arg constructor sets `authorizationProvider = null`, and `InMemoryTaskStore.get(String taskId)` is a bare map lookup with no authorization check regardless of provider:

```java public InMemoryTaskStore() { this.authorizationProvider = null; // default wiring }

@Override public @Nullable Task get(String taskId) { return tasks.get(taskId); // no owner / caller check } ```

Authorization is enforced only when the application both supplies a `TaskAuthorizationProvider` *and* routes requests through `AuthorizationRequestHandlerDecorator` (via CDI), which checks ownership before delegating. A server that uses the default store, or wires `DefaultRequestHandler.builder…