CVE-2026-111771Medium· 6.8▾ SunlitMCP TypeScript SDK: Server bearer authentication accepted tokens issued for another service
▾ Sunlit zone — Low / medium · no exploitation signal
impact 37.4 · likelihood 0 · exploitation 0
Need a working PoC? Pro members can cast a request and our team develops one — it lands right here.
In affected versions, the SDK's server-side bearer authentication had no way to check that a token was issued for your server (its audience). Where one authorization server issues tokens for several services, a valid token for another service was also accepted by your MCP server.
Yes, if your HTTP server uses requireBearerAuth() or verifyBearerToken(), its authorization server also issues tokens for other services, and your verifyAccessToken() does not check the token's audience (aud) itself.
Affected versions:
@modelcontextprotocol/sdk 1.6.0 through 1.31.0@modelcontextprotocol/server 2.0.0 through 2.2.0@modelcontextprotocol/express 2.0.0 through 2.0.1@modelcontextprotocol/server-legacy 2.0.0 through 2.3.0Upgrade to:
@modelcontextprotocol/sdk 1.32.0 or later@modelcontextprotocol/server 2.3.0 or later, together with @modelcontextprotocol/express 2.0.2 or later if you use it@modelcontextprotocol/server-legacy 2.3.1 or laterUpgrading alone changes nothing. The patched versions add an expectedResource setting that is off by default. To turn the check on, make both of these changes together:
requireBearerAuth({ verifier, expectedResource: new URL('https://mcp.example.com/mcp') }).verifyAccessToken() as AuthInfo.resource, also a URL.A token for another service then gets 401. With only the first change, every request gets 401.
If you cannot upgrade yet, reject any token whose aud does not include your server inside verifyAccessToken(). That closes the issue on every version.
@modelcontextprotocol/sdk >= 1.6.0, < 1.32.0@modelcontextprotocol/server >= 2.0.0, < 2.3.0@modelcontextprotocol/express >= 2.0.0, < 2.0.2@modelcontextprotocol/server-legacy >= 2.0.0, < 2.3.1Upgrade to a patched release:
@modelcontextprotocol/sdk 1.32.0@modelcontextprotocol/server 2.3.0@modelcontextprotocol/express 2.0.2@modelcontextprotocol/server-legacy 2.3.1Connected by shared product, vendor, weakness, or advisory.
CVE-2026-111768High· 7.5MCP TypeScript SDK: One HTTP request within the default size limit could exhaust server memory during validation
CVE-2026-111769Medium· 6.5MCP TypeScript client SDK: HTTP client transports and OAuth requests followed cross-origin redirects and re-sent custom headers and request bodies
CVE-2026-111770High· 7.7MCP TypeScript server SDK: Shared transport or server instances delivered one HTTP client's messages to another
CVE-2026-111767High· 8.6MCP TypeScript SDK: Experimental tasks were not tied to the session that created them
CVE-2025-67740Low· 2.7In JetBrains TeamCity before 2025.11 improper access control could expose GitHub App token's metadata
CVE-2026-104850High· 7.5MCP TypeScript SDK is the official TypeScript SDK for Model Context Protocol servers and clients