PatchSiren cyber security CVE debrief

CVE-2025-69196 jlowin CVE debrief

CVE-2025-69196 is a high-severity vulnerability in FastMCP, a framework for building MCP applications. The issue allows an attacker to obtain a token for an MCP server by exploiting the improper handling of the resource parameter in authorization and token requests. This vulnerability has been patched in version 2.14.2. The CVSS score for this vulnerability is 7.4, indicating a high level of severity. The vulnerability was published on March 16, 2026, and last modified on June 30, 2026.

Vendor: jlowin
Product: fastmcp
CVSS: HIGH 7.4
CISA KEV: Not listed in stored evidence
Original CVE published: 2026-03-16
Original CVE updated: 2026-07-15
Advisory published: 2026-03-16
Advisory updated: 2026-07-15

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.

Sources and references

Verified primary and authoritative sources

CVE-2025-69196 CVE Program record
Publisher, destination, and source semantics verified

URL: https://www.cve.org/CVERecord?id=CVE-2025-69196

CVE Program - Official CVE Program record with source-provided CVE metadata.
CVE-2025-69196 NVD vulnerability detail
Publisher, destination, and source semantics verified

URL: https://nvd.nist.gov/vuln/detail/CVE-2025-69196

NIST National Vulnerability Database - Official NIST NVD detail page and source-specific vulnerability assessment.

Supplemental references

Mitigation or vendor reference
Unverified legacy reference

URL: https://github.com/PrefectHQ/fastmcp/security/advisories/GHSA-5h2m-4q8j-pqpj

[email protected] - Exploit, Mitigation, Vendor Advisory
Source reference
Unverified legacy reference

URL: https://access.redhat.com/security/cve/CVE-2025-69196

0b0ca135-0b70-47e7-9f44-1890c2a1c46c
Source reference
Unverified legacy reference

URL: https://security.access.redhat.com/data/csaf/v2/vex/2025/cve-2025-69196.json

0b0ca135-0b70-47e7-9f44-1890c2a1c46c

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.