Auth bypass in Jlowin Fastmcp
CVE-2025-69196
FastMCP is the standard framework for building MCP applications. Prior to version 2.14.2, the server does not properly respect the resource parameter submitted by the client in the authorization and token request. Instead of issuing the token explicitly for the MCP server, the token is issued for the base_url passed to the OAuthProxy during initialization. This issue has been patched 2.14.2.
Vulnerability class: Broken Access Control
EPSS: 0.004 (28.4th percentile) — read the EPSS interpretation.
CVSS v3 metric
CVSS v3 base score 6.5 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N.
Affected products
- Jlowin Fastmcp — versions < 2.14.2
Weakness classification (CWE)
References
- security-advisories@github.com (x_refsource_CONFIRM, Exploit, Mitigation, Vendor Advisory)
- 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
- 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
- 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
- 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
Frequently asked questions
- What is CVE-2025-69196?
- CVE-2025-69196 is a medium-severity vulnerability in Jlowin Fastmcp, classified under Incorrect Authorization. CVSS score: 6.5/10. Published 2026-03-16.
- How severe is CVE-2025-69196?
- Medium severity. CVSS v3 base score is 6.5 out of 10.