---
id: CVE-2026-108586
title: >-
  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
summary: >-
  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 s…
severity: medium
cvss: 5.4
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N'
cwe:
  - CWE-863
published: '2026-10-10'
updated: '2026-10-10'
sourceUpdated: '2026-10-10T17:17:00.593'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-108586'
references:
  - url: 'https://github.com/1mcp-app/agent'
    label: disclosure@vulncheck.com
  - url: >-
      https://github.com/1mcp-app/agent/blob/v0.39.0/src/sdk/legacy/transport/http/middlewares/scopeAuthMiddleware.ts#L163-L183
    label: disclosure@vulncheck.com
  - url: >-
      https://github.com/1mcp-app/agent/blob/v0.39.0/src/transport/http/routes/inspectHelpers.ts#L79-L102
    label: disclosure@vulncheck.com
  - url: 'https://hackmd.io/@haind/1mcp-negated-tag-filter-oauth-scope-bypass'
    label: disclosure@vulncheck.com
  - url: >-
      https://www.vulncheck.com/advisories/1mcp-agent-0.20.0-through-0.39.0-oauth-tag-scope-bypass-via-negated-tag-filter
    label: disclosure@vulncheck.com
tags:
  - nvd
ingestedAt: '2026-10-10T17:28:24.990Z'
---

## Overview

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.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.