# CVE-2026-111771: Model Context Protocol TypeScript SDK: Server bearer authentication accepted tokens issued for another service

Status: published. Published: 2026-11-05. Updated: 2026-11-10.

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 only the expected audience check causes every request to receive HTTP 401. This issue is fixed in @modelcontextprotocol/sdk 1.32.0, @modelcontextprotocol/server 2.3.0, @modelcontextprotocol/express 2.0.2, and @modelcontextprotocol/server-legacy 2.3.1.

## Remediation

- fix: @modelcontextprotocol/sdk (npm): GitHub reports patched versions 1.32.0. Check the advisory for the affected release branch. (source: GitHub GHSA-rvq5-wwqv-78pq) — https://github.com/modelcontextprotocol/typescript-sdk/security/advisories/GHSA-rvq5-wwqv-78pq
- fix: @modelcontextprotocol/server (npm): GitHub reports patched versions 2.3.0. Check the advisory for the affected release branch. (source: GitHub GHSA-rvq5-wwqv-78pq) — https://github.com/modelcontextprotocol/typescript-sdk/security/advisories/GHSA-rvq5-wwqv-78pq
- fix: @modelcontextprotocol/express (npm): GitHub reports patched versions 2.0.2. Check the advisory for the affected release branch. (source: GitHub GHSA-rvq5-wwqv-78pq) — https://github.com/modelcontextprotocol/typescript-sdk/security/advisories/GHSA-rvq5-wwqv-78pq
- fix: @modelcontextprotocol/server-legacy (npm): GitHub reports patched versions 2.3.1. Check the advisory for the affected release branch. (source: GitHub GHSA-rvq5-wwqv-78pq) — https://github.com/modelcontextprotocol/typescript-sdk/security/advisories/GHSA-rvq5-wwqv-78pq
- fix: @modelcontextprotocol/sdk (npm): OSV reports a fixed version 1.32.0. Check the advisory for supported release branches. (source: OSV GHSA-rvq5-wwqv-78pq) — https://github.com/advisories/GHSA-rvq5-wwqv-78pq
- fix: @modelcontextprotocol/server (npm): OSV reports a fixed version 2.3.0. Check the advisory for supported release branches. (source: OSV GHSA-rvq5-wwqv-78pq) — https://github.com/advisories/GHSA-rvq5-wwqv-78pq
- fix: @modelcontextprotocol/express (npm): OSV reports a fixed version 2.0.2. Check the advisory for supported release branches. (source: OSV GHSA-rvq5-wwqv-78pq) — https://github.com/advisories/GHSA-rvq5-wwqv-78pq
- fix: @modelcontextprotocol/server-legacy (npm): OSV reports a fixed version 2.3.1. Check the advisory for supported release branches. (source: OSV GHSA-rvq5-wwqv-78pq) — https://github.com/advisories/GHSA-rvq5-wwqv-78pq

## Affected products and versions

- modelcontextprotocol / typescript-sdk: >= 1.6.0, < 1.32.0 (affected). Source: CNA: GitHub_M
- @modelcontextprotocol / sdk: >= 1.6.0, < 1.32.0 (affected). Source: CNA: GitHub_M
- @modelcontextprotocol / server: >= 2.0.0, < 2.3.0 (affected). Source: CNA: GitHub_M
- @modelcontextprotocol / express: >= 2.0.0, < 2.0.2 (affected). Source: CNA: GitHub_M
- @modelcontextprotocol / server-legacy: >= 2.0.0, < 2.3.1 (affected). Source: CNA: GitHub_M
-  / @modelcontextprotocol/sdk (@modelcontextprotocol/sdk): >= 1.6.0, < 1.32.0 (affected, GitHub advisory range). Source: GitHub GHSA-rvq5-wwqv-78pq
-  / @modelcontextprotocol/server (@modelcontextprotocol/server): >= 2.0.0, < 2.3.0 (affected, GitHub advisory range). Source: GitHub GHSA-rvq5-wwqv-78pq
-  / @modelcontextprotocol/express (@modelcontextprotocol/express): >= 2.0.0, < 2.0.2 (affected, GitHub advisory range). Source: GitHub GHSA-rvq5-wwqv-78pq
-  / @modelcontextprotocol/server-legacy (@modelcontextprotocol/server-legacy): >= 2.0.0, < 2.3.1 (affected, GitHub advisory range). Source: GitHub GHSA-rvq5-wwqv-78pq
-  / @modelcontextprotocol/sdk (@modelcontextprotocol/sdk): ≥ 1.6.0; < 1.32.0 (affected, semver); OSV events: introduced 1.6.0; fixed 1.32.0. Source: OSV GHSA-rvq5-wwqv-78pq
-  / @modelcontextprotocol/server (@modelcontextprotocol/server): ≥ 2.0.0; < 2.3.0 (affected, semver); OSV events: introduced 2.0.0; fixed 2.3.0. Source: OSV GHSA-rvq5-wwqv-78pq
-  / @modelcontextprotocol/express (@modelcontextprotocol/express): ≥ 2.0.0; < 2.0.2 (affected, semver); OSV events: introduced 2.0.0; fixed 2.0.2. Source: OSV GHSA-rvq5-wwqv-78pq
-  / @modelcontextprotocol/server-legacy (@modelcontextprotocol/server-legacy): ≥ 2.0.0; < 2.3.1 (affected, semver); OSV events: introduced 2.0.0; fixed 2.3.1. Source: OSV GHSA-rvq5-wwqv-78pq

## Severity and prioritization

- CVSS 3.1: 6.8 (medium); CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:N; source: CNA: GitHub_M

- CVSS 3.1: 6.8 (medium); CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:N; source: NVD: security-advisories@github.com

- CISA KEV: No listing in collected sources

- EPSS: 0.54% as of 2026-11-09; percentile 45.79%

- SSVC: exploitation none; automatable no; technical impact total; source ADP: CISA-ADP

- Weaknesses: CWE-863

## Exploit evidence

No exploit evidence in collected sources. This is not proof of no exploitation.

## References

- https://github.com/modelcontextprotocol/typescript-sdk/security/advisories/GHSA-rvq5-wwqv-78pq (CNA: GitHub_M; x_refsource_CONFIRM)

- https://github.com/modelcontextprotocol/typescript-sdk/pull/2929 (CNA: GitHub_M; x_refsource_MISC)

- https://github.com/modelcontextprotocol/typescript-sdk/pull/2930 (CNA: GitHub_M; x_refsource_MISC)

- https://github.com/modelcontextprotocol/typescript-sdk/pull/2952 (CNA: GitHub_M; x_refsource_MISC)

- https://github.com/modelcontextprotocol/typescript-sdk/commit/40f8f4e229d963cd7fd2890bda2aeebe7005299a (CNA: GitHub_M; x_refsource_MISC)

- https://github.com/modelcontextprotocol/typescript-sdk/commit/5a0724d14cf34a27a3b070224d2996cdd611df9f (CNA: GitHub_M; x_refsource_MISC)

- https://github.com/modelcontextprotocol/typescript-sdk/commit/5a1867390b91b8836f49af76c45427279f513325 (CNA: GitHub_M; x_refsource_MISC)

- https://github.com/modelcontextprotocol/typescript-sdk/releases/tag/1.32.0 (CNA: GitHub_M; x_refsource_MISC)

- https://github.com/modelcontextprotocol/typescript-sdk/releases/tag/@modelcontextprotocol/express@2.0.2 (CNA: GitHub_M; x_refsource_MISC)

- https://github.com/modelcontextprotocol/typescript-sdk/releases/tag/@modelcontextprotocol/server-legacy@2.3.1 (CNA: GitHub_M; x_refsource_MISC)

- https://github.com/modelcontextprotocol/typescript-sdk/releases/tag/@modelcontextprotocol/server@2.3.0 (CNA: GitHub_M; x_refsource_MISC)

- https://github.com/modelcontextprotocol/typescript-sdk/commit/40f8f4e229d963cd7fd2890bda2aeebe7005299a (security-advisories@github.com)

- https://github.com/modelcontextprotocol/typescript-sdk/commit/5a0724d14cf34a27a3b070224d2996cdd611df9f (security-advisories@github.com)

- https://github.com/modelcontextprotocol/typescript-sdk/commit/5a1867390b91b8836f49af76c45427279f513325 (security-advisories@github.com)

- https://github.com/modelcontextprotocol/typescript-sdk/pull/2929 (security-advisories@github.com)

- https://github.com/modelcontextprotocol/typescript-sdk/pull/2930 (security-advisories@github.com)

- https://github.com/modelcontextprotocol/typescript-sdk/pull/2952 (security-advisories@github.com)

- https://github.com/modelcontextprotocol/typescript-sdk/releases/tag/1.32.0 (security-advisories@github.com)

- https://github.com/modelcontextprotocol/typescript-sdk/releases/tag/@modelcontextprotocol/express@2.0.2 (security-advisories@github.com)

- https://github.com/modelcontextprotocol/typescript-sdk/releases/tag/@modelcontextprotocol/server-legacy@2.3.1 (security-advisories@github.com)

- https://github.com/modelcontextprotocol/typescript-sdk/releases/tag/@modelcontextprotocol/server@2.3.0 (security-advisories@github.com)

- https://github.com/modelcontextprotocol/typescript-sdk/security/advisories/GHSA-rvq5-wwqv-78pq (security-advisories@github.com)

- https://github.com/modelcontextprotocol/typescript-sdk/security/advisories/GHSA-rvq5-wwqv-78pq (GitHub Security Advisories; advisory)

- https://github.com/advisories/GHSA-rvq5-wwqv-78pq (OSV / GitHub Security Advisories; advisory)

- https://osv.dev/vulnerability/GHSA-rvq5-wwqv-78pq (OSV / GitHub Security Advisories; osv)

## Provenance

- CNA: GitHub_M: https://www.cve.org/CVERecord?id=CVE-2026-111771; retrieved 2026-11-10; source updated 2026-11-10

- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-111771; retrieved 2026-11-10; source updated 2026-11-10

- GitHub Security Advisories: https://github.com/modelcontextprotocol/typescript-sdk/security/advisories/GHSA-rvq5-wwqv-78pq; retrieved 2026-11-07; source updated 2026-10-19

- OSV / GitHub Security Advisories: https://osv.dev/vulnerability/GHSA-rvq5-wwqv-78pq; retrieved 2026-11-05; source updated 2026-10-20

- FIRST EPSS: https://api.first.org/data/v1/epss?cve=CVE-2026-111771; retrieved 2026-11-10; source updated Not reported

Revision: 89b5429f468a57452fb0a1b8cb95abecf2c5dcac1bd3988ded7bdb4d91560c41

Canonical: https://y2.dev/cve/CVE-2026-111771

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