CVE-2026-108586

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.

References

https://www.vulncheck.com/advisories/1mcp-agent-0.20.0-through-0.39.0-oauth-tag-scope-bypass-via-negated-tag-filter

https://hackmd.io/@haind/1mcp-negated-tag-filter-oauth-scope-bypass

https://github.com/1mcp-app/agent/blob/v0.39.0/src/transport/http/routes/inspectHelpers.ts#L79-L102

https://github.com/1mcp-app/agent/blob/v0.39.0/src/sdk/legacy/transport/http/middlewares/scopeAuthMiddleware.ts#L163-L183

https://github.com/1mcp-app/agent

https://euvd.enisa.europa.eu/vulnerability/EUVD-2026-96373

Details

Source: Mitre, NVD

Risk Information

CVSS v2

CVSS v3

CVSS v4

EPSS