Authorization Bypass in 1MCP Agent by 1MCP
CVE-2026-108586

5.3MEDIUM

Key Information:

Vendor

1mcp-app

Status
@1mcp/agent
Vendor
CVE Published:
10 October 2026

What is CVE-2026-108586?

The 1MCP Agent (versions 0.20.0 to 0.39.0) contains a flaw that allows authenticated users to circumvent OAuth tag-scope enforcement. By leveraging negated advanced tag-filter expressions, attackers with a single-tag token are able to manipulate filters, thus gaining access to backend MCP servers outside their authorized scopes. This unauthorized access can lead to disclosure of sensitive data or further exploitation of backend services, highlighting the critical importance of properly enforcing authentication and authorization mechanisms.

Affected Version(s)

@1mcp/agent 0.20.0 <= 0.39.0

References

https://hackmd.io/@haind/1mcp-negated-tag-filter-oauth-sc...
third-party-advisory
https://github.com/1mcp-app/agent/blob/v0.39.0/src/sdk/le...
technical-description
https://github.com/1mcp-app/agent/blob/v0.39.0/src/transp...
technical-description

CVSS V4

Score:
5.3
Severity:
MEDIUM
Confidentiality:
Low
Integrity:
Low
Availability:
None
Attack Vector:
Network
Attack Complexity:
Low
Attack Required:
None
Privileges Required:
Undefined
User Interaction:
None

Timeline

  • Vulnerability published

  • Vulnerability Reserved

Credit

HaiND from the Post and Telecommunication Institute of Technology
.