Description
1MCP Agent (@1mcp/agent) 0.20.0 through 0.39.0 contains an incorrect authorization vulnerability that allows authenticated clients to bypass OAuth tag-scope enforcement using negated advanced tag-filter expressions. Attackers holding a single-tag token can send a filter like not <granted-tag> to list and invoke tools on backend MCP servers outside their granted scopes.
Affected products
| Vendor | Product | Affected | Fixed |
|---|---|---|---|
| 1mcp-app | @1mcp/agent | 0.20.0 – ≤ 0.39.0 | — |
References
- https://hackmd.io/@haind/1mcp-negated-tag-filter-oauth-scope-bypass third-party-advisory
- https://github.com/1mcp-app/agent/blob/v0.39.0/src/sdk/legacy/transport/http/middlewares/scopeAuthMiddleware.ts#L163-L183 technical-description
- https://github.com/1mcp-app/agent/blob/v0.39.0/src/transport/http/routes/inspectHelpers.ts#L79-L102 technical-description
- https://github.com/1mcp-app/agent product
- VulnCheck Advisory: 1MCP Agent 0.20.0 through 0.39.0 OAuth Tag-Scope Bypass via Negated Tag Filter third-party-advisory