vulnerability / NVI-00011938 / Revision 1
MCP TypeScript client SDK: HTTP client transports and OAuth requests followed cross-origin redirects and re-sent custom headers and request bodies
GitHub lists this reviewed advisory for @modelcontextprotocol/sdk, @modelcontextprotocol/client. Published version ranges and source prerequisites are shown below; this is not an inspection of a visitor’s application.
This report has not inspected your inventory, configuration, deployed build, reachability or evidence. A catalog listing and a severity score do not establish exposure or compromise.
01 / Meaning
Why it matters
Published affected context helps an owner decide what evidence to gather. This report has not examined your application.
6.5 medium
GitHub source severity; exploitability and local consequence require separate evidence.
As of · GitHub Advisory Database
02 / Applicability
The affected context
Affected versions, configuration prerequisites and known exclusions are public. Confirm each one against the deployed service.
@modelcontextprotocol/sdk
source listed< 1.32.0
### 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 instea
@modelcontextprotocol/client
source listed>= 2.0.0, < 2.3.0
### 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 instea
03 / Response
What to do next
- investigate
Identify the exact component and deployed version, examine the linked publisher’s conditions, and retain evidence of any mitigation.
Confirm current vendor support, compatibility and deployment evidence. This report has not tested a fix in your system. GitHub Advisory Database
A fixed release is not deployment evidence.
Check current vendor support and compatibility. After making a change, verify the deployed build and relevant runtime conditions. Keep the evidence, owner and time. An updated lockfile alone does not prove what is running.
04 / Limits
What this report cannot establish
- Customer inventory, deployment, reachability and exploitation have not been inspected.
05 / Provenance
Sources you can inspect
Each assertion retains its source. Mirrored records may repeat one underlying publisher; additional links are not independent corroboration.
- GHSA-6prh-2h8m-c8cw ↗
GitHub Advisory Database · vendor advisory
Observed . GitHub Advisory Database; CC-BY-4.0. Each advisory links its original attribution. Null normalizes fields.
Public revision history
Only published revisions appear here. Routine fetches do not create a material-change event.
- Revision 1 ·
First indexed by Null; source disclosure date is shown separately.