CVE-2026-27124: FastMCP is the standard framework for building MCP applications

Q: How do I fix CVE-2026-27124?

fastmcp: upgrade to 3.2.0. Exact commands for each OS are on this page.

Q: Is CVE-2026-27124 being exploited?

CVE-2026-27124 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2026-27124 affect?

CVE-2026-27124 affects fastmcp. Severity is medium (CVSS 6.1). FastMCP is the standard framework for building MCP applications. Prior to version 3.2.0, while testing the GitHubProvider OAuth integration, which allows authentication to a FastMCP MCP server via a FastMCP OAuthProxy using GitHub OAuth, it

Q: How urgent is CVE-2026-27124?

Priority 29/100. Public exploit reference

Routine

MEDIUM 6.1UPGRADE

CVE-2026-27124 is a medium-severity flaw (CVSS 6.1) affecting fastmcp. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

FastMCP is the standard framework for building MCP applications. Prior to version 3.2.0, while testing the GitHubProvider OAuth integration, which allows authentication to a FastMCP MCP server via a FastMCP OAuthProxy using GitHub OAuth, it was discovered that the FastMCP OAuthProxy does not properly validate the user's consent upon receiving the authorization code from GitHub. In combination with GitHub’s behavior of skipping the consent page fo

Why this priority

Public exploit reference

A fixed release or distro patch exists.

Risk facts

CVSS score	6.1 (Medium)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	Required
EPSS exploit chance	0.2% (top 89%)
CISA exploited list	No
Weakness	CWE-441
Published	2026-04-03
Last modified	2026-07-24

Publisher (CNA): GitHub, Inc. · Vendor: jlowin

Last updated 2026-07-24 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-04-03 16:16 UTCPublished CVE record published
2026-07-24 22:10 UTCUpdated Record last modified

jlowin fastmcp UPGRADE

Affected: < 3.2.0

Fixed in: 3.2.0

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy fastmcp || rpm -q fastmcp || fastmcp --version

2. UPGRADE to 3.2.0 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade fastmcp

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade fastmcp

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-27124?

fastmcp: upgrade to 3.2.0. Exact commands for each OS are on this page.

Is CVE-2026-27124 being exploited?

CVE-2026-27124 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-27124 affect?

CVE-2026-27124 affects fastmcp. Severity is medium (CVSS 6.1). FastMCP is the standard framework for building MCP applications. Prior to version 3.2.0, while testing the GitHubProvider OAuth integration, which allows authentication to a FastMCP MCP server via a FastMCP OAuthProxy using GitHub OAuth, it

How urgent is CVE-2026-27124?

Priority 29/100. Public exploit reference

Software pages

GitHub vulnerabilities

Related CVEs

CVE-2026-32871 CRITICAL 10.0 UPGRADE FastMCP is a Pythonic way to build MCP servers and clients
CVE-2025-64340 MEDIUM 6.7 UPGRADE FastMCP is the standard framework for building MCP applications
CVE-2025-69196 MEDIUM 6.5 UPGRADE FastMCP is the standard framework for building MCP applications

References

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