CVE-2026-111771 (GCVE-0-2026-111771)

Vulnerability from cvelistv5 – Published: 2026-11-05 21:08 – Updated: 2026-11-05 21:08
VLAI
Title
Model Context Protocol TypeScript SDK: Server bearer authentication accepted tokens issued for another service
Summary
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.
Severity
6.8 (Medium)
CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:N
CWE
  • CWE-863 - Incorrect Authorization
Assigner
GitHub_M CNA under the mitre root
CNA scorecard C 72/100 over 8026 records in the last 180 days details
References
Impacted products
Show details on NVD website
To clipboard 

{
  "containers": {
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      "affected": [
        {
          "product": "typescript-sdk",
          "vendor": "modelcontextprotocol",
          "versions": [
            {
              "status": "affected",
              "version": "\u003e= 1.6.0, \u003c 1.32.0"
            }
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          "product": "sdk",
          "vendor": "@modelcontextprotocol",
          "versions": [
            {
              "status": "affected",
              "version": "\u003e= 1.6.0, \u003c 1.32.0"
            }
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        {
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          "vendor": "@modelcontextprotocol",
          "versions": [
            {
              "status": "affected",
              "version": "\u003e= 2.0.0, \u003c 2.3.0"
            }
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        },
        {
          "product": "express",
          "vendor": "@modelcontextprotocol",
          "versions": [
            {
              "status": "affected",
              "version": "\u003e= 2.0.0, \u003c 2.0.2"
            }
          ]
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        {
          "product": "server-legacy",
          "vendor": "@modelcontextprotocol",
          "versions": [
            {
              "status": "affected",
              "version": "\u003e= 2.0.0, \u003c 2.3.1"
            }
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      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "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\u0027s 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."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "attackComplexity": "HIGH",
            "attackVector": "NETWORK",
            "availabilityImpact": "NONE",
            "baseScore": 6.8,
            "baseSeverity": "MEDIUM",
            "confidentialityImpact": "HIGH",
            "integrityImpact": "HIGH",
            "privilegesRequired": "LOW",
            "scope": "UNCHANGED",
            "userInteraction": "NONE",
            "vectorString": "CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:N",
            "version": "3.1"
          }
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "cweId": "CWE-863",
              "description": "CWE-863: Incorrect Authorization",
              "lang": "en",
              "type": "CWE"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-11-05T21:08:55.758Z",
        "orgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
        "shortName": "GitHub_M"
      },
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          "tags": [
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          "url": "https://github.com/modelcontextprotocol/typescript-sdk/security/advisories/GHSA-rvq5-wwqv-78pq"
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          "tags": [
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          "url": "https://github.com/modelcontextprotocol/typescript-sdk/pull/2952"
        },
        {
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          "tags": [
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          "url": "https://github.com/modelcontextprotocol/typescript-sdk/commit/40f8f4e229d963cd7fd2890bda2aeebe7005299a"
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          "tags": [
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          "url": "https://github.com/modelcontextprotocol/typescript-sdk/commit/5a0724d14cf34a27a3b070224d2996cdd611df9f"
        },
        {
          "name": "https://github.com/modelcontextprotocol/typescript-sdk/commit/5a1867390b91b8836f49af76c45427279f513325",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/modelcontextprotocol/typescript-sdk/commit/5a1867390b91b8836f49af76c45427279f513325"
        },
        {
          "name": "https://github.com/modelcontextprotocol/typescript-sdk/releases/tag/1.32.0",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/modelcontextprotocol/typescript-sdk/releases/tag/1.32.0"
        },
        {
          "name": "https://github.com/modelcontextprotocol/typescript-sdk/releases/tag/@modelcontextprotocol/express@2.0.2",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/modelcontextprotocol/typescript-sdk/releases/tag/@modelcontextprotocol/express@2.0.2"
        },
        {
          "name": "https://github.com/modelcontextprotocol/typescript-sdk/releases/tag/@modelcontextprotocol/server-legacy@2.3.1",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/modelcontextprotocol/typescript-sdk/releases/tag/@modelcontextprotocol/server-legacy@2.3.1"
        },
        {
          "name": "https://github.com/modelcontextprotocol/typescript-sdk/releases/tag/@modelcontextprotocol/server@2.3.0",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/modelcontextprotocol/typescript-sdk/releases/tag/@modelcontextprotocol/server@2.3.0"
        }
      ],
      "source": {
        "advisory": "GHSA-rvq5-wwqv-78pq",
        "discovery": "UNKNOWN"
      },
      "title": "Model Context Protocol TypeScript SDK: Server bearer authentication accepted tokens issued for another service"
    }
  },
  "cveMetadata": {
    "assignerOrgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
    "assignerShortName": "GitHub_M",
    "cveId": "CVE-2026-111771",
    "datePublished": "2026-11-05T21:08:55.758Z",
    "dateReserved": "2026-10-16T17:52:09.082Z",
    "dateUpdated": "2026-11-05T21:08:55.758Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
    "nvd": {
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        "affected": [
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                "vendor": "modelcontextprotocol",
                "versions": [
                  {
                    "status": "affected",
                    "version": "\u003e= 1.6.0, \u003c 1.32.0"
                  }
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              },
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                "vendor": "@modelcontextprotocol",
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                    "status": "affected",
                    "version": "\u003e= 1.6.0, \u003c 1.32.0"
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              {
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                "vendor": "@modelcontextprotocol",
                "versions": [
                  {
                    "status": "affected",
                    "version": "\u003e= 2.0.0, \u003c 2.3.0"
                  }
                ]
              },
              {
                "product": "express",
                "vendor": "@modelcontextprotocol",
                "versions": [
                  {
                    "status": "affected",
                    "version": "\u003e= 2.0.0, \u003c 2.0.2"
                  }
                ]
              },
              {
                "product": "server-legacy",
                "vendor": "@modelcontextprotocol",
                "versions": [
                  {
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                    "version": "\u003e= 2.0.0, \u003c 2.3.1"
                  }
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          }
        ],
        "cveTags": [],
        "descriptions": [
          {
            "lang": "en",
            "value": "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\u0027s 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."
          }
        ],
        "id": "CVE-2026-111771",
        "lastModified": "2026-11-05T21:18:35.973",
        "metrics": {
          "cvssMetricV31": [
            {
              "cvssData": {
                "attackComplexity": "HIGH",
                "attackVector": "NETWORK",
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                "vectorString": "CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:N",
                "version": "3.1"
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              "impactScore": 5.2,
              "source": "security-advisories@github.com",
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          }
        ],
        "sourceIdentifier": "security-advisories@github.com",
        "vulnStatus": "Received",
        "weaknesses": [
          {
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              {
                "lang": "en",
                "value": "CWE-863"
              }
            ],
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            "type": "Primary"
          }
        ]
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    },
    "redhat_vex": {
      "aggregate_severity": "Moderate",
      "current_release_date": "2026-11-06T07:14:31+00:00",
      "cve": "CVE-2026-111771",
      "id": "CVE-2026-111771",
      "initial_release_date": "2026-11-05T21:08:55.758000+00:00",
      "product_status:known_not_affected": "3",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "@modelcontextprotocol/sdk: @modelcontextprotocol/server: @modelcontextprotocol/express: @modelcontextprotocol/server-legacy: Model Context Protocol TypeScript SDK: Authentication bypass via missing token audience validation",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-111771.json",
      "version": "3"
    }
  }
}



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