CVE-2026-111771: MCP TypeScript SDK accepted bearer tokens issued for other services

# CVE-2026-111771: MCP TypeScript SDK accepted bearer tokens issued for other services

https://gcdradar.vercel.app/incidents/cve-2026-111771-mcp-typescript-sdk-accepted-bearer-tokens-is · AIR-2026-1433 · closed 2026-10-20

- Lane: Patch now
- Severity: 2 (Disclosed vulnerability)
- Fix status: Fix status unknown
- First reported: 2026-10-20
- AI role: Attack on AI
- Products: MCP TypeScript SDK
- CVE ids: CVE-2026-111771
- CVSS: 6.8

## Summary

Server-side bearer authentication in the MCP TypeScript SDK failed to validate the audience claim of incoming tokens. Consequently, MCP servers could accept valid tokens issued for entirely different services if they shared an authorization server.

## What to do

No action recorded; read the sources below and the vendor's advisory.

## Latest updates

- 2026-11-05: NVD record published (https://nvd.nist.gov/vuln/detail/CVE-2026-111771)
- 2026-10-20: CVE-2026-111771: MCP TypeScript SDK: Server bearer authentication accepted tokens issued for another service (https://github.com/advisories/GHSA-rvq5-wwqv-78pq)

## Sources

- 2026-10-20 GitHub Advisory Database: CVE-2026-111771: MCP TypeScript SDK: Server bearer authentication accepted tokens issued for another service https://github.com/advisories/GHSA-rvq5-wwqv-78pq
- 2026-11-05 NVD: CVE-2026-111771: The Model Context Protocol TypeScript SDK provides TypeScript client and server implementations of the Model Context Protocol. https://nvd.nist.gov/vuln/detail/CVE-2026-111771

Verify against the vendor's advisory before changing production. Data CC BY-SA 4.0, https://gcdradar.vercel.app.