The A2A Java SDK exposes sensitive bearer tokens and authentication credentials when parsing requests fails. During a protobuf deserialization error in RestHandler.parseRequestBody, the SDK logs the entire JSON request body at SEVERE level. An attacker who can force the parsing to fail, such as by sending a malformed push notification configuration, causes those credentials to appear in the server logs in cleartext. This flaw directly results in the disclosure of credentials that could be used to authenticate to the client push notification endpoint, enabling potential forgery of task status updates. The vulnerability is an instance of CWE‑532, logging sensitive information.

The flaw affects the a2aproject a2a-java SDK for Java, specifically all releases prior to 1.3.0.Final. Versions 1.3.0.Final and later contain a fix that prevents the entire request body from being logged when deserialization fails. The affected component is RestHandler in the transport/rest handler package of the SDK.

The CVSS base score of 5.7 indicates a moderate severity, reflecting limited impact scope and requirement for the attacker to interact with the affected API endpoint. No EPSS score is reported, and the vulnerability is not listed in the CISA KEV catalog, suggesting that active exploitation is not currently documented. Nevertheless, an attacker who can target the /v1/tenants/{tenant}/tasks/{taskId}/pushNotificationConfigs endpoint and induce a parsing error can read the logged credentials if they have access to the server logs or a log aggregation system. The attacker then could replay or forge push notifications to compromise client systems. The vulnerability would be most easily exploited against systems with public or inadequately protected REST interfaces and where log retention or aggregation is accessible.