Is there a public exploit for CVE-2026-111771?

No public exploit for CVE-2026-111771 was found in Exploit-DB, Metasploit, Nuclei templates or public proof-of-concept repositories. That is an absence of evidence rather than proof that none exists.

How severe is CVE-2026-111771?

CVE-2026-111771 scores CVSS 6.8 (v3.1), rated medium. EPSS puts the chance of exploitation in the next 30 days at 0.54%.

What does CVE-2026-111771 affect?

CVE-2026-111771 affects @modelcontextprotocol, modelcontextprotocol typescript-sdk, Server, SDK, server-legacy, express. It is part of the AI and agent stack (Model Context Protocol).

6.8 Medium

The Model Context Protocol TypeScript SDK provides TypeScript client and server implementations of the Model Context Protocol.

CVE-2026-111771

The Model Context Protocol TypeScript SDK provides TypeScript client and server implementations of the Model Context Protocol. From 1.6.0 until 1.32.0 in @modelcontextprotocol/sdk, from 2.0.0 until 2.3.0 in @modelcontextprotocol/server, from 2.0.0 until 2.0.2 in @modelcontextprotocol/express, and from 2.0.0 until 2.3.1 in @modelcontextprotocol/server-legacy, server-side bearer authentication could accept a valid access token issued for a different service because the SDK did not enforce the token audience. The affected surface is server-side HTTP bearer authentication. The trigger is a valid token whose audience names another service. The authorization server must issue tokens for multiple services, and the application's verifyAccessToken() must not independently validate aud. Applications already validating aud inside verifyAccessToken() are not affected. An attacker with a token for another service could authenticate to the MCP server and obtain the confidentiality and integrity capabilities granted to an authenticated caller. Upgrading alone leaves the new audience validation disabled. Operators must enable audience validation and provide the token audience together. Enabling…

Part of the AI stack

This affects Model Context Protocol, in MCP & tool servers.

Assessment

CVSS: 6.8 (v3.1)
Severity: Medium
EPSS: 0.54% chance of exploitation in the next 30 days
Known exploited: Not listed in CISA KEV
Exploit availability: Nothing found in Exploit-DB, Metasploit, Nuclei or public PoC repositories
Published: 5 November 2026
Last updated: 10 November 2026
Affected: @modelcontextprotocol · modelcontextprotocol · SDK · Server · express · server-legacy
Assigner: GitHub_M

CVSS vectorCVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:N

At the source

EUVD (ENISA)

References

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