CVE-2026-108586

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.

CVSS v3 5.4 MEDIUM

5.4^/10

CVSS v3 : MEDIUM

Vector :

Exploitability : 2.8 / Impact : 2.5

Attack Vector NETWORK

Attack Complexity LOW

Privileges Required LOW

User Interaction NONE

Confidentiality Impact LOW

Integrity Impact LOW

Availability Impact NONE

Scope UNCHANGED

References

Link	Resource
https://github.com/1mcp-app/agent
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/blob/v0.39.0/src/transport/http/routes/inspectHelpers.ts#L79-L102
https://hackmd.io/@haind/1mcp-negated-tag-filter-oauth-scope-bypass
https://www.vulncheck.com/advisories/1mcp-agent-0.20.0-through-0.39.0-oauth-tag-scope-bypass-via-negated-tag-filter

Configurations

No configuration.

History

10 Oct 2026, 17:17

Type	Values Removed	Values Added
New CVE

Information

Published : 2026-10-10 17:17

Updated : 2026-10-16 19:21

NVD link : CVE-2026-108586

Mitre link : CVE-2026-108586

CVE.ORG link : CVE-2026-108586

JSON object : View

Products Affected

No product.

CWE

CWE-863

Incorrect Authorization

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