---
id: "CVE-2026-116477"
kind: "vulnerability"
aliases: ["CVE-2026-116477"]
title: "a2a-dotnet: JSON-RPC parser error messages expose internal details to remote callers"
severity: "medium"
cvss: 5.3
epss: null
exploited: false
status: "open"
category: "package"
products: []
ecosystems: []
tags: ["a2a-dotnet", "asp.net-core", "dotnet", "package", "self-hosted"]
not_affected_if: ["default-config"]
published_at: "2026-10-26T20:17:54+00:00"
first_seen_at: "2026-10-26T20:50:17+00:00"
updated_at: "2026-10-26T20:51:53+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-116477", "first_seen_at": "2026-10-26T20:50:17+00:00"}]
---

# a2a-dotnet: JSON-RPC parser error messages expose internal details to remote callers

The A2A .NET SDK's JSON-RPC request processor returns error messages that reveal internal information when handling crafted requests. A remote attacker can read that information from the responses.

_Summary, check and fix written by a model from the sources; labelled as such._

## How to check

- Check the installed `A2A` package version in the project's NuGet references (for example `dotnet list package`); versions up to `1.0.0-preview2` are affected.
- Check whether the service hosts the A2A JSON-RPC endpoint via the ASP.NET Core integration in `src/A2A.AspNetCore/A2AJsonRpcProcessor.cs`.

## Fix

- Upgrade the a2a-dotnet package to `1.0.0-preview3` or later, per the patch `ccbd12b6108a6a8f0fd5d8b4a9ece3c8a94ba1e4`.

## Timeline

- 2026-10-26T20:50:17+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-116477

## From the sources

A security vulnerability has been detected in a2aproject a2a-dotnet up to 1.0.0-preview2. The impacted element is the function A2AJsonRpcProcessor.ProcessRequestAsync of the file src/A2A.AspNetCore/A2AJsonRpcProcessor.cs of the component Parser. The manipulation leads to information exposure through error message. It is possible to initiate the attack remotely. Upgrading to version 1.0.0-preview3 is sufficient to resolve this issue. The identifier of the patch is ccbd12b6108a6a8f0fd5d8b4a9ece3c8a94ba1e4. Upgrading the affected component is recommended.

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_Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai_