CVE-2026-108586CWE-863broken-access-control

CVE-2026-108586

Medium · published October 10, 2026

CVSS v3.1
5.4
EPSS
0%
Percentile
8.2
In the wild
Unconfirmed
What it is

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.

The record
Technical detail
CVSS v3.1
5.4 · MEDIUM
Vector
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N
CVSS v4.0
5.3 · CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N
EPSS
0.00190 · 8.2th percentile
Weakness
CWE-863 · Incorrect Authorization
Published
2026-10-10T21:17Z
References (5)
https://github.com/1mcp-app/agent · [email protected]https://github.com/1mcp-app/agent/blob/v0.39.0/src/sdk/legacy/transport/http/middlewares/scopeAuthMiddleware.ts#L163-L183 · [email protected]https://github.com/1mcp-app/agent/blob/v0.39.0/src/transport/http/routes/inspectHelpers.ts#L79-L102 · [email protected]https://hackmd.io/@haind/1mcp-negated-tag-filter-oauth-scope-bypass · [email protected]https://www.vulncheck.com/advisories/1mcp-agent-0.20.0-through-0.39.0-oauth-tag-scope-bypass-via-negated-tag-filter · [email protected]
EPSS history
Timeline
  • 12 OCT 03:26Z
    EPSS moved — → 0%
    epss
  • 10 OCT 16:14Z
    1MCP Agent 0.20.0 through 0.39.0 OAuth Tag-Scope Bypass via Negated Tag Filter
    cvelistv5
  • 10 OCT 16:14Z
    1MCP Agent 0.20.0 through 0.39.0 OAuth Tag-Scope Bypass via Negated Tag Filter
    cvelistv5