# CVE-2026-90820: a2aproject a2a-java authorization bypass in onListTasks

Source: https://junglewise.ai/threats/cve-2026-90820-a2aproject-a2a-java-authorization-bypass-in-onlisttasks  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-09-14. Updated: 2026-09-26  
License: CC BY 4.0 with a link back

CVE-2026-90820 · Severity: medium · CVSS 4.3 · Published 2026-09-14

a2a-java is a Java SDK for the Agent2Agent protocol used for secure task and workflow management. A vulnerability in the onListTasks function fails to perform required authorization checks, allowing an attacker to bypass access controls and list tasks they should not be permitted to view.

Technologies: [A2aproject A2a-Java](https://junglewise.ai/threats/technologies/a2a-java). Vendors: [A2aproject](https://junglewise.ai/threats/vendors/a2aproject).

## Quick answers

**Is CVE-2026-90820 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-90820 being exploited in the wild.

**How severe is CVE-2026-90820?** Medium severity, with a CVSS score of 4.3, published 14 September 2026.

**Which products and versions are affected?** A2aproject A2a-Java 1.2.0.

**Is there a fix for CVE-2026-90820?** A patch was published on 2026-09-14: Fix available in version 1.3.0 (commit e9a1abf9c90c02b16d17293afdc3cc2f555d63a6) Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-90820 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-90820?** Check whether you run A2aproject A2a-Java at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

The vulnerability is an authorization bypass in the AuthorizationRequestHandlerDecorator.onListTasks method. Unlike other handler methods, onListTasks delegated directly to the underlying handler without performing authorization checks before exposing the list of tasks. The flaw allows a remote attacker to call onListTasks and retrieve a complete task list regardless of their permissions. The fix adds a list-scoped checkRead authorization check using an empty-string sentinel for the whole list scope before delegation. This vulnerability requires network access to the a2a-java service but does not require authentication or user interaction beyond a direct method call.

## Affected products

- a2aproject a2a-java 1.2.0

## Timeline

- 2026-09-14: disclosed
- 2026-09-14: patched: Fix available in version 1.3.0 (commit e9a1abf9c90c02b16d17293afdc3cc2f555d63a6)

## References

- [https://github.com/a2aproject/a2a-java/](https://github.com/a2aproject/a2a-java/)
- [https://github.com/a2aproject/a2a-java/commit/e9a1abf9c90c02b16d17293afdc3cc2f555d63a6](https://github.com/a2aproject/a2a-java/commit/e9a1abf9c90c02b16d17293afdc3cc2f555d63a6)

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