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NVD Vulnerability Details :
CVE-2026-27124
Analyzed
More InfoOfficial Page
Source-security-advisories@github.com
View Known Exploited Vulnerability (KEV) details
Published At-03 Apr, 2026 | 16:16
Updated At-22 Apr, 2026 | 14:37

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 for previously authorized clients, this introduces a Confused Deputy vulnerability. This issue has been patched in version 3.2.0.

CISA Catalog
Date AddedDue DateVulnerability NameRequired Action
N/A
Date Added: N/A
Due Date: N/A
Vulnerability Name: N/A
Required Action: N/A
Metrics
TypeVersionBase scoreBase severityVector
Secondary4.08.2HIGH
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/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
Primary3.16.1MEDIUM
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
Type: Secondary
Version: 4.0
Base score: 8.2
Base severity: HIGH
Vector:
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/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
Type: Primary
Version: 3.1
Base score: 6.1
Base severity: MEDIUM
Vector:
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
CPE Matches
jlowin
jlowin
>>fastmcp>>Versions before 3.2.0(exclusive)
cpe:2.3:a:jlowin:fastmcp:*:*:*:*:*:*:*:*
Weaknesses
CWE IDTypeSource
CWE-441Secondarysecurity-advisories@github.com
CWE ID: CWE-441
Type: Secondary
Source: security-advisories@github.com
Evaluator Description
Evaluator Impact

Evaluator Solution

Vendor Statements
References
HyperlinkSourceResource
https://github.com/PrefectHQ/fastmcp/security/advisories/GHSA-rww4-4w9c-7733security-advisories@github.com
Exploit
Mitigation
Vendor Advisory
https://github.com/PrefectHQ/fastmcp/security/advisories/GHSA-rww4-4w9c-7733134c704f-9b21-4f2e-91b3-4a467353bcc0
Exploit
Mitigation
Vendor Advisory
Hyperlink: https://github.com/PrefectHQ/fastmcp/security/advisories/GHSA-rww4-4w9c-7733
Source: security-advisories@github.com
Resource:
Exploit
Mitigation
Vendor Advisory
Hyperlink: https://github.com/PrefectHQ/fastmcp/security/advisories/GHSA-rww4-4w9c-7733
Source: 134c704f-9b21-4f2e-91b3-4a467353bcc0
Resource:
Exploit
Mitigation
Vendor Advisory
Change History
0Changes found
Details not found