# CVE-2026-116476: a2aproject a2a-dotnet race condition in TaskProjection.ApplyStatus

Source: https://junglewise.ai/threats/cve-2026-116476-a-weakness-has-been-identified-in-a2aproject-a2a-dotnet-up-to-1  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-10-26. Updated: 2026-10-26  
License: CC BY 4.0 with a link back

CVE-2026-116476 · Severity: medium · CVSS 5.4 · Published 2026-10-26

a2a-dotnet is a C#/.NET SDK for the A2A protocol used for task coordination and remote operations. A race condition in the TaskProjection.ApplyStatus function allows concurrent requests to bypass terminal-state checks, potentially causing tasks to be incorrectly re-opened or receive duplicate cancellations, leading to inconsistent state and operational disruption. An attacker with remote access to the task service can exploit this by sending concurrent state-mutation requests.

Vendors: [A2aproject](https://junglewise.ai/threats/vendors/a2aproject).

## Quick answers

**Is CVE-2026-116476 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-116476 being exploited in the wild.

**How severe is CVE-2026-116476?** Medium severity, with a CVSS score of 5.4, published 26 October 2026.

**Which products and versions are affected?** A2aproject A2a-Dotnet up to 1.0.0-preview3.

**Is there a fix for CVE-2026-116476?** No fixed version is recorded yet. Restrict remote network access to the task service to trusted agents only, and avoid sending concurrent state-mutation or cancel requests for the same task until a patch is available.</anigation>
</invoke> If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**How is CVE-2026-116476 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-116476?** Check whether you run A2aproject A2a-Dotnet 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.

## How to fix


Restrict remote network access to the task service to trusted agents only, and avoid sending concurrent state-mutation or cancel requests for the same task until a patch is available.</anigation>
</invoke>

## Technical details

The vulnerability is a time-of-check-time-of-use (TOCTOU) race condition in the CancelTaskAsync method and state-mutation functions of TaskProjection. The affected code reads task state and validates terminal status without holding a per-task lock, allowing concurrent requests to both pass validation before either commits the state change. This permits terminal tasks (COMPLETED, CANCELED, FAILED, REJECTED) to be incorrectly mutated back to earlier states or to receive duplicate handlers. The race affects CancelTaskAsync, ApplyStatus, and ApplyMessage operations on remote network access.

## Affected products

- a2aproject a2a-dotnet up to 1.0.0-preview3

## Timeline

- 2026-10-26: disclosed

## References

- [https://github.com/a2aproject/a2a-dotnet/](https://github.com/a2aproject/a2a-dotnet/)
- [https://github.com/a2aproject/a2a-dotnet/pull/453](https://github.com/a2aproject/a2a-dotnet/pull/453)

## Related threats

- [a2aproject a2a-dotnet information exposure in JSON-RPC error messages](https://junglewise.ai/threats/cve-2026-116477-a-security-vulnerability-has-been-detected-in-a2aproject-a2a)