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Vulnerability · Published Nov 5, 2026 · Assigned by GitHub_M

CVE-2026-111769Model Context Protocol TypeScript SDK: HTTP client transports and OAuth requests followed cross-origin redirects and re-sent custom headers and request bodies

Medium 6.5

In plain English

A medium-severity information exposure in client from @modelcontextprotocol. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.4% (higher than 35% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 3.1)6.5Medium
Exploit odds (30 days)0.4%top 65.1% of all CVEs
Exploited in the wildNo reportsnot in CISA KEV
Attack toolingNoneno public tooling known

Official description

The Model Context Protocol TypeScript SDK provides TypeScript client and server implementations of the Model Context Protocol. Prior to 1.32.0 in @modelcontextprotocol/sdk and from 2.0.0 until 2.3.0 in @modelcontextprotocol/client, the HTTP client transports and OAuth client requests followed redirects to a different origin while retaining custom request headers and, for HTTP 307 or 308 responses, request bodies. The affected surfaces are StreamableHTTPClientTransport, SSEClientTransport, and OAuth client functions such as auth(). The trigger is an HTTP redirect to another origin. Custom headers and mcp-session-id can be re-sent to the redirected origin. HTTP 307 and 308 redirects can also re-send the request body. OAuth request bodies can contain refresh_token and client_secret values. Current runtimes already strip the Authorization header across origins. stdio clients do not use the affected HTTP path. A malicious or compromised MCP or authorization server could therefore receive API keys, session identifiers, OAuth refresh tokens, or OAuth client secrets. Restoring unrestricted redirect following after upgrading restores the exposure. This issue is fixed in @modelcontextprotocol/sdk 1.32.0 and @modelcontextprotocol/client 2.3.0.

Affected packages & fixed versions

EcosystemPackageFixed inAdvisory
npm@modelcontextprotocol/client2.3.0GHSA-6prh-2h8m-c8cw
npm@modelcontextprotocol/sdk1.32.0GHSA-6prh-2h8m-c8cw

Affected products (as reported)

VendorProductVersions
modelcontextprotocol typescript-sdk < 1.32.0
@modelcontextprotocol sdk < 1.32.0
@modelcontextprotocol client >= 2.0.0, < 2.3.0

Weakness: CWE-200 · Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:L/A:N

References