CVE-2026-104850

MCP TypeScript SDK is the official TypeScript SDK for Model Context Protocol servers and clients. Starting in version 1.12.0 and prior to versions 1.31.0 and 2.2.0, the SDK's OAuth client support let the MCP server a client connected to decide which authorization server received the client's OAuth credentials. Stored and pre-provisioned credentials were not bound to the authorization server they belong to. A malicious or compromised MCP server could name its own authorization server in its protected resource metadata. Without any user interaction, the client would send that server the refresh_token and client_secret stored from an earlier sign-in (1.x), or the configured client_secret or signed assertion of a bundled non-interactive provider (1.x and 2.x). Only those applications that use the SDK as an MCP client over HTTP with an authProvider: your own OAuthClientProvider, or the bundled ClientCredentialsProvider, PrivateKeyJwtProvider, StaticPrivateKeyJwtProvider or (2.x) CrossAppAccessProvider and that may connect to an MCP server the owners does not fully trust while holding credentials for a legitimate authorization server are affected. @modelcontextprotocol/sdk 1.31.0 (1.x) and @modelcontextprotocol/client 2.2.0 (2.x) patch the issue. A workaround for those who cannot upgrade is available. 2.0.0 and 2.1.0 already accept expectedIssuer. On 1.x, the only workaround is to connect OAuth-enabled clients only to MCP servers you trust.

Database specific

{
    "cna_assigner": "GitHub_M",
    "cwe_ids": [
        "CWE-345",
        "CWE-522"
    ],
    "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/104xxx/CVE-2026-104850.json"
}

References

Affected packages

Git / github.com/modelcontextprotocol/typescript-sdk

Affected ranges

Type

GIT

Repo

https://github.com/modelcontextprotocol/typescript-sdk

Events

Introduced

0c4b3082751e1ec387a2f8ddbfe6a8c882d2ce0f

Fixed

4b0051f400219f8d8855f9a5433c6df35f15a639

Introduced

cc4b41617ce3601b1290d67216ea0b194a3cd9ac

Fixed

dd22ba25ddbe7cd8822e1fe9c738a974996a28f6

Database specific

Show details

{
    "extracted_events": [
        {
            "introduced": "1.12.0"
        },
        {
            "fixed": "1.31.0"
        },
        {
            "introduced": "2.0.0"
        },
        {
            "fixed": "2.2.0"
        }
    ],
    "source": "AFFECTED_FIELD"
}

Affected versions

0.*

0.15.1

1.*

1.12.0

1.12.1

1.12.2

1.12.3

1.13.0

1.13.1

1.13.2

1.13.3

1.14.0

1.15.0

1.15.1

1.16.0

1.17.0

1.17.1

1.17.2

1.17.3

1.17.4

1.17.5

1.18.0

1.18.1

1.18.2

1.19.0

1.20.0

1.20.1

1.20.2

1.21.0

1.21.1

1.22.0

1.23.0

1.23.0-beta.0

1.24.0

1.24.1

1.24.2

1.24.3

1.25.0

1.25.1

1.30.0

1.30.1

@modelcontextprotocol/client@2.*

@modelcontextprotocol/client@2.0.0

@modelcontextprotocol/client@2.1.0

@modelcontextprotocol/codemod@2.*

@modelcontextprotocol/codemod@2.0.0

@modelcontextprotocol/codemod@2.1.0

@modelcontextprotocol/core@2.*

@modelcontextprotocol/core@2.0.0

@modelcontextprotocol/core@2.1.0

@modelcontextprotocol/express@2.*

@modelcontextprotocol/express@2.0.0

@modelcontextprotocol/express@2.0.1

@modelcontextprotocol/fastify@2.*

@modelcontextprotocol/fastify@2.0.0

@modelcontextprotocol/hono@2.*

@modelcontextprotocol/hono@2.0.0

@modelcontextprotocol/hono@2.0.1

@modelcontextprotocol/node@2.*

@modelcontextprotocol/node@2.0.0

@modelcontextprotocol/node@2.1.0

@modelcontextprotocol/server-legacy@2.*

@modelcontextprotocol/server-legacy@2.0.0

@modelcontextprotocol/server-legacy@2.1.0

@modelcontextprotocol/server@2.*

@modelcontextprotocol/server@2.0.0

@modelcontextprotocol/server@2.1.0

v1.*

v1.25.2

v1.26.0

v1.27.0

v1.27.1

v1.28.0

v1.29.0

Database specific

source

"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-104850.json"