8 results · Feed
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Medium 6.5
Unbounded response body buffering in Streamable HTTP clients
Before 3.9.0, the built-in Streamable HTTP clients in rmcp read non-streaming HTTP response bodies into memory with no size limit. Both the reqwest client (`transport-streamable-http-client-reqwest`) and the Unix socket client (`transport-streamable-http-clie…
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Unscored —
OAuth client SSRF filter checks host strings, not resolved addresses
From 2.0.0 until 3.7.0, the rmcp OAuth client decided whether it may fetch an authorization server's metadata URL by inspecting only the host string. It rejected literal loopback, private and link-local IP addresses and known cloud metadata hostnames, but it …
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High 7.5
Unbounded tool schema cache in Streamable HTTP server transport
From 3.0.0 until 3.6.0, `StreamableHttpService` cached the result of `ServerHandler::get_tool` in a process-wide map keyed by the tool name of incoming `tools/call` requests. The map had no size limit and no eviction, and it also cached unknown tool names. An…
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Medium —
rmcp OAuth client fetches server-controlled resource_metadata URLs
## Summary The `rmcp` OAuth client accepts a server-controlled `resource_metadata=` URL from the `WWW-Authenticate` header and fetches it without same-origin or private-network validation. An attacker-controlled MCP server can return a `401 WWW-Authenticate: …
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Medium 6.8
RMCP: Custom HTTP headers leak to cross-origin redirect targets
RMCP is an official Rust SDK for the Model Context Protocol. Prior to 2.1.0, the rmcp crate's StreamableHttpClientTransport in crates/rmcp/src/transport/common/reqwest/streamable_http_client.rs builds its default_http_client with reqwest's automatic redirect …
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High 8.2
RMCP: Missing Resource Field Validation in OAuth Protected Resource Metadata Discovery
RMCP is an official Rust SDK for the Model Context Protocol. Prior to 2.0.0, the rmcp crate's OAuth implementation in crates/rmcp/src/transport/auth.rs omits the RFC 9728 resource field from ResourceServerMetadata and allows discover_oauth_server_via_resource…
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High 7.5
RMCP: Unauthenticated permanent session-table leak in rmcp Streamable HTTP server transport leads to remote denial-of-service
RMCP is an official Rust SDK for the Model Context Protocol. Prior to 2.0.0, the rmcp crate's stateful Streamable HTTP server in crates/rmcp/src/transport/streamable_http_server/tower.rs allows an unauthenticated client to send a well-formed JSON-RPC POST tha…
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High 8.8CVE-2026-42559 Public exploit
RMCP: DNS rebinding vulnerability in rmcp Streamable HTTP server transport
RMCP is an official Rust SDK for the Model Context Protocol. Prior to version 1.4.0, the rmcp crate's Streamable HTTP server transport (crates/rmcp/src/transport/streamable_http_server/) did not validate the incoming Host header. This allowed a malicious publ…