A2A Java SDK EUVD-2026-110079

Exploitation requires reaching an a2a-java server endpoint (the Quarkus-based JSON-RPC or REST routes, e.g. invokeJSONRPCHandler/sendMessage/getTask, or the gRPC handler) and causing an internal exception during request processing so the error handler constructs InternalError from t.getMessage(); the raw exception message is then returned to the caller. Per the vendor vector (PR:L) the attacker needs low-level privileges, though the actual authentication requirement depends on how the A2A server is deployed and secured. Limiting factors: impact is confined to disclosure of internal exception message text (low confidentiality, no integrity/availability impact), the attacker must be able to induce a server-side error, and the issue is fully remediated only by upgrading to 1.3.0.Final - the fix also preserves the detail server-side via logging rather than returning it to the client.

This is a genuine but low-severity information-disclosure issue (CWE-209), not a high-priority emergency. The VulDB-supplied CVSS 4.0 vector (AV:N/AC:L/AT:N/PR:L/UI:N/VC:L/VI:N/VA:N) scores 5.3 and indicates a remotely reachable, low-complexity flaw that requires some privileges (PR:L) and yields only low confidentiality impact with no integrity or availability effect. The supporting signals agree on low real-world urgency: EPSS is 0.32% (24th percentile), there is no CISA KEV listing, and no confirmed working exploit code is present in the input. The vuln.today decision label is 'this_month' rather than act_now/emergency, consistent with a patch-when-convenient posture. SSVC-style framing: exploitation is not observed, technical impact is partial (leakage of internal exception text only), and while the endpoint is network-automatable in principle, the payoff is limited to error-message disclosure. The source diff confirms the exact mechanism (returning t.getMessage() to the client), so the issue is real and well-understood, but its impact ceiling is low. One note of tension: the vendor sets PR:L, yet whether the A2A server endpoints require authentication depends on deployment, so the privilege requirement should be verified against your own configuration.

An attacker with access to an a2a-java JSON-RPC or REST endpoint (Quarkus reference server) sends a request crafted to trigger an internal exception during processing; the server returns an InternalError whose message is the raw exception text (t.getMessage()), potentially leaking internal details such as class names, file paths, or backend state. No confirmed working exploit code is available, but the trigger is straightforward given the source diff. The disclosed information could aid reconnaissance for further attacks but does not by itself grant code execution or data modification.