{"cve":"CVE-2026-63128","nvd":{"published":"2026-09-16T15:17:39.960","modified":"2026-09-30T17:51:56.193","status":"Deferred","description":"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 that is not an initialization request, or an initialization request with a mismatched protocol header, causing StreamableHttpService::handle_post to call LocalSessionManager.create_session before validating the message. An early validation failure returns without removing the inserted LocalSessionHandle from LocalSessionManager.sessions, permanently retaining session and channel state for the server process lifetime. Repeated requests can grow the shared session table without bound, degrade legitimate-client latency through lock contention, exhaust memory, and terminate the server. This issue is fixed in version 2.0.0.","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","score":7.5},"cwes":["CWE-400","CWE-401","CWE-772"],"references":["https://github.com/modelcontextprotocol/rust-sdk/commit/dfa7fd6f9309deab60bea230b041be9a3fcda846","https://github.com/modelcontextprotocol/rust-sdk/pull/934","https://github.com/modelcontextprotocol/rust-sdk/releases/tag/rmcp-v2.0.0","https://github.com/modelcontextprotocol/rust-sdk/security/advisories/GHSA-9pj6-vhgr-3mwh","https://github.com/modelcontextprotocol/rust-sdk/security/advisories/GHSA-9pj6-vhgr-3mwh"],"products":[],"source":"nvd","synced_at":"2026-10-19T22:54:41.405518556+00:00"},"epss":{"cve":"CVE-2026-63128","score":0.00535,"percentile":0.44881,"date":"2026-10-25"},"kev":null,"osv":[{"id":"GHSA-9pj6-vhgr-3mwh","url":"https://osv.dev/vulnerability/GHSA-9pj6-vhgr-3mwh","summary":"RMCP: Unauthenticated permanent session-table leak in rmcp Streamable HTTP server transport leads to remote denial-of-service","modified":"2026-09-16T22:30:08.343637534Z","packages":[{"ecosystem":"crates.io","name":"rmcp","purl":"pkg:cargo/rmcp","ranges":["<2.0.0"],"fixed":["2.0.0"]}]}],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}