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CVE-2026-53709 – Authentication Bypass via Hardcoded JWT Secret (Admin Token Forgery) – IBM ContextF

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Summary

CVE-2026-53709 is a critical authentication bypass vulnerability caused by a hardcoded default JWT signing key in IBM ContextForge MCP Gateway (mcp-context-forge). A remote, unauthenticated attacker can forge valid administrator tokens without a database account. The CVSS v3.1 base score is 9.8 (Critical).

Technical details

  • Root cause: Versions before 1.0.2 ship a known default JWT_SECRET_KEY in mcpgateway/config.py and .env.example (CWE-287, CWE-321, CWE-798, CWE-1188).
  • Trigger conditions: verify_jwt_token() accepts HS256 tokens signed with the known key. get_current_user() creates a platform administrator when the token subject matches PLATFORM_ADMIN_EMAIL and REQUIRE_USER_IN_DB is false. The deployment must still be using the default signing key.
  • Attack vector: Network; no privileges and no user interaction required.
  • Impact: An attacker can mint accepted administrator tokens and gain platform administrator access, with high impact on confidentiality, integrity and availability. While the vulnerable signing key stays configured and the platform-admin bootstrap stays enabled, forged access survives password rotation, account deletion and session revocation.

Affected software

  • IBM mcp-context-forge (ContextForge MCP Gateway): all versions prior to 1.0.2

Severity

  • CVSS v3.1 base score: 9.8 (Critical)
  • Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Mitigation and recommended actions

  • Immediate: Upgrade to version 1.0.2 or later. IBM’s separate bulletin on default credentials in the same product recommends upgrading to v1.0.10.
  • Set a strong, unique JWT_SECRET_KEY and strong administrator passwords. Do not rely on the defaults.
  • The advisory lists no other workarounds. Until patched, restrict network access to the gateway.
  • Treat deployments that ran with the default key as potentially compromised. Rotate the signing key, because forged tokens remain valid for as long as the old key is configured.

References

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