Security context

What an agent needs to avoid regressing past fixes and find the next vuln in this repo.

modelcontextprotocol/python-sdk

              main @ 2713b53
            

Fixes

CVEs

HIGH

Peak severity

Highlights

Auth Bypass: 9 prior fixes. Scrutinize any change in this area.

src/mcp/client/auth/oauth2.py: most-fixed (5 issues). Treat as high-risk during review.

7 high-severity fixes in this history; regressions here are high-impact.

Recurring patterns

The bug types that recur here, drawn from past fixes, not open vulnerabilities.

Auth Bypass: Multiple issues in OAuth2 flow allow credential reuse, issuer mix-ups, and token leakage due to missing validation of authorization server metadata, issuer parameters, and dynamic registration bounds.

Denial of Service: The JSON-RPC communication channel is highly sensitive to crashes. Unhandled schema-validation exceptions during request/notification parsing can terminate the main message loop and crash the entire process.

Auth Bypass: Unbound SSE and Streamable HTTP transport sessions allowed unauthorized users to access, intercept, or send commands to active streams belonging to other authenticated principals.