What’s Vulnerable › Vulnerabilities

CVE-2025-69196: FastMCP OAuth Proxy token reuse across MCP servers

• Severity: medium (CVSS 6.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.4% probability of exploitation in the next 30 days
• Public exploit or detection template: yes
• Published: 2026-03-16 · updated 2026-07-15
• Weakness: CWE-863

Description

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.

Affected products

• jlowin fastmcp: before 2.14.2 — fixed in 2.14.2

How to fix

Upgrade to a fixed version: jlowin fastmcp 2.14.2. Check the vendor advisory for mitigations.

References

• https://github.com/PrefectHQ/fastmcp/security/advisories/GHSA-5h2m-4q8j-pqpj
• https://access.redhat.com/errata/RHSA-2026:36350
• https://access.redhat.com/security/cve/CVE-2025-69196
• https://bugzilla.redhat.com/show_bug.cgi?id=2448179
• https://security.access.redhat.com/data/csaf/v2/vex/2025/cve-2025-69196.json

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