{"items":[{"id":"NVI-00013257","kind":"vulnerability","title":"rmcp OAuth client fetches server-controlled resource_metadata URLs","revision":1,"unknowns":["Customer inventory, deployment, reachability and exploitation have not been inspected."],"lifecycle":"active","identifiers":["GHSA-c9xm-49cp-xcr9"],"plain_summary":"GitHub lists this reviewed advisory for rmcp. Published version ranges and source prerequisites are shown below; this is not an inspection of a visitor’s application.","review_status":"source_listed","control_topics":[],"public_actions":[{"summary":"Identify the exact component and deployed version, examine the linked publisher’s conditions, and retain evidence of any mitigation.","source_ids":["sr-a8b4798e97637160b24a4bcab59e0bd5"],"action_type":"investigate","limitations":"Confirm current vendor support, compatibility and deployment evidence. This report has not tested a fix in your system.","current_supported_target":null}],"schema_version":"1.1.0","source_metrics":[],"why_it_matters":"Published affected context helps an owner decide what evidence to gather. This report has not examined your application.","related_sources":[{"id":"sr-a8b4798e97637160b24a4bcab59e0bd5","url":"https://github.com/advisories/GHSA-c9xm-49cp-xcr9","basis":"vendor_advisory","notes":"GitHub Advisory Database; CC-BY-4.0. Each advisory links its original attribution. Null normalizes fields.","title":"GHSA-c9xm-49cp-xcr9","publisher":"GitHub Advisory Database","observed_at":"2026-11-01T01:40:00.567Z"}],"affected_context":[{"certainty":"source_listed","source_ids":["sr-a8b4798e97637160b24a4bcab59e0bd5"],"technology":"rmcp","known_exclusions":[],"conditions_summary":"## Summary\n\nThe `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.\n\nAn attacker-controlled MCP server can return a `401 WWW-Authenticate: Bearer resource_metadata=\"...\"` header pointing at an internal URL, including localhost, RFC 1918 addresses, or cloud metadata endpoints. The client then performs an outbound GET to that URL from the victim application's network context.\n\n## Affected version\n\n- Repository: `modelcontextprotocol/rust-sdk`\n- Crate: `rmcp`\n- Current `main` reviewed: `c330fede90e4729c234f8e87fdbc5ea27a1dd10c`\n- Commit date: 2026-05-19\n- Affected file: `crates/rmcp/src/transport/auth.rs`\n- File blob: `3aa3e91310662c409af9dc38c9d584d6df217e9c`\n- Severity framing: High/Medium SSRF, depending on the embedding application's network position and whether response parsing gives the attacker useful success/failure or chained fetch behavior.\n\n## Source evidence\n\n`extract_www_authenticate_params()` accepts an absolute URL from the server-controlled header:\n\n```rust\nlet resource_key = \"resource_metadata=\";\nwhile let Some(pos) = header_lowercase[search_offset","public_affected_ranges":["< 2.0.0"]}],"null_published_at":"2026-11-01T07:29:12.932Z","source_updated_at":"2026-10-02T16:12:32.000Z","source_disclosed_at":"2026-10-02T16:12:31.000Z","is_synthetic_fixture":false,"null_last_reviewed_at":null,"public_change_summary":"First indexed by Null; source disclosure date is shown separately.","null_first_observed_at":"2026-11-01T01:40:00.567Z"}],"next_cursor":null,"snapshot_revision":"42594"}