# CVE-2026-116684: Model Context Protocol Python SDK: Server bearer-token authentication accepts tokens issued for a different resource server


- **Severity:** Medium 6.8 (`CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:N`)
- **Exploited in the wild:** Not known
- **Fix available:** Yes
- **Published:** 27 Oct 2026
- **Updated:** 27 Oct 2026
- **Also known as:** GHSA-w4fh-qvv9-3v23

## What is CVE-2026-116684?

CVE-2026-116684 is a medium-severity vulnerability in modelcontextprotocol python-sdk, published on 27 Oct 2026. 

### Official description

The Model Context Protocol Python SDK is the official Python SDK for Model Context Protocol servers and clients. From 1.10.0 until 1.30.0 and 2.2.0, server-side bearer authentication configured through AuthSettings with token_verifier accepts a valid token issued for another service when the authorization server serves multiple resources and the TokenVerifier does not independently validate the aud audience. This resource-confusion flaw lets a token holder authenticate to the wrong MCP server and exercise that token's resulting access. This issue is fixed in versions 1.30.0 and 2.2.0.

Weakness: CWE-863 (Incorrect Authorization)

## Which versions are affected by CVE-2026-116684?

4 open source packages ship an affected version, including mcp.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `mcp` | PyPI | From 1.10.0 | 1.30.0 |
| `mcp` | PyPI | From 1.10.0 | 1.30.0 |
| `mcp` | PyPI | From 2.0.0 | 2.2.0 |
| `mcp` | PyPI | From 2.0.0 | 2.2.0 |

## How do I fix CVE-2026-116684?

Upgrade mcp to a fixed version for your release line: 1.30.0 or 2.2.0.

## Is CVE-2026-116684 being exploited?

There is no known exploitation of CVE-2026-116684 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-116684 and fix it if it is affected.

What it is: CVE-2026-116684 is a medium-severity vulnerability in modelcontextprotocol python-sdk, published on 27 Oct 2026. 
Exploitation: There is no known exploitation of CVE-2026-116684 in the wild and no public exploit code.

Affected packages and fixed versions:
- mcp (PyPI): affected from 1.10.0; fixed in 1.30.0
- mcp (PyPI): affected from 1.10.0; fixed in 1.30.0
- mcp (PyPI): affected from 2.0.0; fixed in 2.2.0
- mcp (PyPI): affected from 2.0.0; fixed in 2.2.0

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-116684/ (Markdown: https://insights.sbomify.com/CVE-2026-116684/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-116684
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-116684
- OSV: https://osv.dev/vulnerability/CVE-2026-116684

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-116684/
Summaries are generated and may contain mistakes; the official description above is the record.