CVE-2026-116684 Model Context Protocol Python SDK: Server bearer-token authentication accepts tokens issued for a different resource server
- Exploited in the wild
- Not known
- Fix
- Available
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
Which versions are affected by CVE-2026-116684?
4 open source packages ship an affected version, including mcp.
| Package | 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.
Sources
Also known as GHSA-w4fh-qvv9-3v23.