GHSA-6prh-2h8m-c8cw

Source

https://github.com/advisories/GHSA-6prh-2h8m-c8cw

Import Source

https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/10/GHSA-6prh-2h8m-c8cw/GHSA-6prh-2h8m-c8cw.json

JSON Data

https://api.osv.dev/v1/vulns/GHSA-6prh-2h8m-c8cw

Aliases

CVE-2026-111769

Published

2026-10-20T18:26:30Z

Modified

2026-10-20T18:45:09Z

Severity

6.5 (Medium) CVSS_V3 - CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:L/A:N CVSS Calculator

Summary

MCP TypeScript client SDK: HTTP client transports and OAuth requests followed cross-origin redirects and re-sent custom headers and request bodies

Details

Summary

In affected versions, the SDK's HTTP client transports and OAuth requests followed redirects to any origin.

If an MCP server or authorization server redirected a request to another origin, that origin received custom request headers (such as an X-API-Key set in requestInit.headers) and the mcp-session-id header. On a 307 or 308 it also received the request body, including OAuth token requests with their refresh_token and client_secret.

On current runtimes fetch already drops the Authorization header across origins.

Am I affected?

Yes, if your application uses StreamableHTTPClientTransport, SSEClientTransport, or the SDK's OAuth client functions such as auth(). stdio clients are not affected.

Affected versions:

@modelcontextprotocol/sdk all versions through 1.31.0
@modelcontextprotocol/client 2.0.0 through 2.2.0

Fix

Upgrade to:

1.x: @modelcontextprotocol/sdk 1.32.0 or later
2.x: @modelcontextprotocol/client 2.3.0 or later

Redirects are now followed only within the same origin, and not at all in browsers. If your MCP server or authorization server redirects to another origin on purpose, configure the final URL instead. Setting redirectPolicy: 'follow' on a transport restores the old behaviour and the exposure.

If a redirect may have reached a host you do not control, rotate the API keys and client_secret your application held and revoke its tokens.

If you cannot upgrade yet, pass a fetch that refuses redirects, for example (url, init) => fetch(url, { ...init, redirect: 'error' }).

Database specific

{
    "cwe_ids":  [
        "CWE-200"
    ],
    "github_reviewed":  true,
    "github_reviewed_at":  "2026-10-20T18:26:30Z",
    "nvd_published_at":  null,
    "severity":  "MODERATE"
}

References

Affected packages

npm / @modelcontextprotocol/sdk

Package

Name: @modelcontextprotocol/sdk; View open source insights on deps.dev
Purl: pkg:npm/%40modelcontextprotocol/sdk

Affected ranges

Type: SEMVER
Events: Introduced

0 Unknown introduced version / All previous versions are affected

Fixed

1.32.0

Database specific

source

"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/10/GHSA-6prh-2h8m-c8cw/GHSA-6prh-2h8m-c8cw.json"

npm / @modelcontextprotocol/client

Package

Name: @modelcontextprotocol/client; View open source insights on deps.dev
Purl: pkg:npm/%40modelcontextprotocol/client

Affected ranges

Type: SEMVER
Events: Introduced

2.0.0

Fixed

2.3.0

Database specific

source

"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/10/GHSA-6prh-2h8m-c8cw/GHSA-6prh-2h8m-c8cw.json"