CVE-2026-111769
Model Context Protocol SDK Arbitrary Redirect Information Disclosure
Description
### 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' })`.
INFO
Published Date :
Oct. 20, 2026, 6:26 p.m.
Last Modified :
Oct. 20, 2026, 6:26 p.m.
Remotely Exploit :
Yes !
Source :
github-security-advisories
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS 3.1 | MEDIUM | github |
Solution
- Upgrade SDK to 1.32.0 or later.
- Upgrade client to 2.3.0 or later.
- Rotate API keys and secrets if redirected.
- Configure final URLs for cross-origin redirects.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-111769.
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-111769 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-111769
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
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The following list is the news that have been mention
CVE-2026-111769 vulnerability anywhere in the article.