CVE-2025-69196 jlowin CVE debrief

Who should care

Organizations using FastMCP version prior to 2.14.2 should be concerned about this vulnerability. The vulnerability allows an attacker to obtain a token for an MCP server, which could lead to unauthorized access. Defender should prioritize patching to version 2.14.2 or later. Additionally, defenders should review their inventory of affected systems and apply compensating controls if necessary.

Technical summary

The vulnerability in FastMCP arises from the server not properly respecting the resource parameter submitted by the client in authorization and token requests. Instead of issuing a token explicitly for the MCP server, the token is issued for the base_url passed to the OAuthProxy during initialization. This issue can be exploited by an attacker to obtain a token for an MCP server. The vulnerability has been patched in version 2.14.2. The CVSS vector for this vulnerability is CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:A/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X.

Defensive priority

Defenders should prioritize patching to version 2.14.2 or later. Additionally, defenders should review their inventory of affected systems and apply compensating controls if necessary.

Recommended defensive actions

• Patch FastMCP to version 2.14.2 or later
• Review inventory of affected systems
• Apply compensating controls if necessary
• Monitor for suspicious activity
• Update incident response plans

Evidence notes

The vulnerability was published on March 16, 2026, and last modified on June 30, 2026. The CVSS score for this vulnerability is 7.4, indicating a high level of severity. The vulnerability has been patched in version 2.14.2.

Official resources