The A2A Java SDK fails to enforce authorization when reading tasks from its InMemoryTaskStore by default. The constructor for the default store sets the authorizationProvider to null, so calling get(String taskId) returns the task without checking the caller or the owner. This allows an adversary to read a task’s status, context ID, message history, and artifacts for any task ID they know or guess, exposing potentially sensitive information. The vulnerability originates from an improper default configuration that skips authorization checks.

The affected product is the A2A Java SDK by the A2APROJECT project. Versions prior to 1.3.0.Final are vulnerable. The default or reference transport endpoints in those releases do not enforce authentication, so the task‑read disclosure is reachable by an unauthenticated remote caller.

The vulnerability carries a CVSS score of 7.5, indicating moderate to high severity. EPSS data is not available, and the issue is not listed in the CISA KEV catalog. The likely attack vector is remote, because the default transport endpoints expose an unauthenticated API for task reads. An attacker with network access who can guess a task ID can retrieve confidential task information without prior authentication. The risk is significant for multi‑caller deployments where task data may be private to each caller.