# Improper handling of null Unicode character when parsing JSON in github.com/modelcontextprotocol/go-sdk

Source: https://junglewise.ai/threats/improper-handling-of-null-unicode-character-when-parsing-json-in-github-27191820  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-03-19  
License: CC BY 4.0 with a link back

Severity: medium · CVSS 4 · Published 2026-03-19

Improper handling of null Unicode character when parsing JSON in github.com/modelcontextprotocol/go-sdk

Technologies: [github.com/modelcontextprotocol/go-sdk (Go)](https://junglewise.ai/threats/technologies/github-com-modelcontextprotocol-go-sdk). Vendors: [Go](https://junglewise.ai/threats/vendors/go).

## Quick answers

**Is This vulnerability exploited in the wild?** No. Junglewise Threat Intelligence has no report of This vulnerability being exploited in the wild.

**How severe is This vulnerability?** Medium severity, with a CVSS score of 4, published 19 March 2026.

**Which products and versions are affected?** github.com/modelcontextprotocol/go-sdk (Go) SEMVER:introduced=0,fixed=1.4.1.

**Is there a fix for This vulnerability?** Yes. github.com/modelcontextprotocol/go-sdk (Go): upgrade to 1.4.1 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**Am I affected?** Check whether you run github.com/modelcontextprotocol/go-sdk (Go) 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

- github.com/modelcontextprotocol/go-sdk (Go): upgrade to 1.4.1 or later

  ```sh
  go get github.com/modelcontextprotocol/go-sdk@v1.4.1
  ```


## Affected products

- github.com/modelcontextprotocol/go-sdk (Go) SEMVER:introduced=0,fixed=1.4.1

## Related threats

- [modelcontextprotocol go-sdk DNS rebinding in HTTP handlers](https://junglewise.ai/threats/cve-2026-34742-modelcontextprotocol-go-sdk-dns-rebinding-in-http-handlers)
- [GO-2026-4770 - Improper handling of null Unicode character when parsing JSON in github.com/modelcontextprotocol/go-sdk](https://junglewise.ai/threats/go-2026-4770-improper-handling-of-null-unicode-character-when-parsing-6cff319e)
- [GO-2026-4773 - Cross-Site Tool Execution for HTTP Servers without Authorizatrion in github.com/modelcontextprotocol/go-sdk](https://junglewise.ai/threats/cve-2026-33252-cross-site-tool-execution-for-http-servers-without-authorizatrion)
- [Model Context Protocol Go SDK improper case sensitivity in JSON-RPC parsing](https://junglewise.ai/threats/cve-2026-27896-model-context-protocol-go-sdk-improper-case-sensitivity-in-json)