CVE-2025-4144

PKCE was implemented in the OAuth implementation in workers-oauth-provider that is part of MCP framework https://github.com/cloudflare/workers-mcp . However, it was found that an attacker could cause the check to be skipped. Fixed in: https://github.com/cloudflare/workers-oauth-provider/pull/27 https://github.com/cloudflare/workers-oauth-provider/pull/27 Impact: PKCE is a defense-in-depth mechanism against certain kinds of attacks and was an optional extension in OAuth 2.0 which became required in the OAuth 2.1 draft. (Note that the MCP specification requires OAuth 2.1.). This bug completely bypasses PKCE protection.

CVSS v3 9.8 CRITICAL

9.8^/10

CVSS v3 : CRITICAL

V3 Legend

Vector :

Exploitability : 3.9 / Impact : 5.9

Attack Vector NETWORK

Attack Complexity LOW

Privileges Required NONE

User Interaction NONE

Confidentiality Impact HIGH

Integrity Impact HIGH

Availability Impact HIGH

Scope UNCHANGED

References

Link	Resource
https://github.com/cloudflare/workers-oauth-provider/pull/27	Issue Tracking Patch

Configurations

Configuration 1 (hide)

cpe:2.3:a:cloudflare:workers-oauth-provider:0.0.5:*:*:*:*:*:*:*

History

12 May 2025, 19:39

Type	Values Removed	Values Added
Summary		(es) PKCE se implementó en la implementación de OAuth en workers-oauth-provider, que forma parte del framework MCP (https://github.com/cloudflare/workers-mcp). Sin embargo, se detectó que un atacante podría omitir la comprobación. Corregido en: https://github.com/cloudflare/workers-oauth-provider/pull/27 https://github.com/cloudflare/workers-oauth-provider/pull/27 Impacto: PKCE es un mecanismo de defensa en profundidad contra ciertos tipos de ataques y era una extensión opcional en OAuth 2.0, que se convirtió en obligatoria en el borrador de OAuth 2.1. (Tenga en cuenta que la especificación MCP requiere OAuth 2.1). Este error ignora por completo la protección de PKCE.
CWE		NVD-CWE-noinfo
CPE		cpe:2.3:a:cloudflare:workers-oauth-provider:0.0.5:::::::*
CVSS	v2 : ~~unknown~~ v3 : ~~unknown~~	v2 : unknown v3 : 9.8
First Time		Cloudflare Cloudflare workers-oauth-provider
References	~~() https://github.com/cloudflare/workers-oauth-provider/pull/27 -~~	() https://github.com/cloudflare/workers-oauth-provider/pull/27 - Issue Tracking, Patch

01 May 2025, 01:15

Type	Values Removed	Values Added
New CVE

Information

Published : 2025-05-01 01:15

Updated : 2025-05-12 19:39

NVD link : CVE-2025-4144

Mitre link : CVE-2025-4144

CVE.ORG link : CVE-2025-4144

JSON object : View

Products Affected

cloudflare

workers-oauth-provider

CWE

CWE-287

Improper Authentication

NVD-CWE-noinfo

{"id": "CVE-2025-4144", "cveTags": [], "metrics": {"cvssMetricV31": [{"type": "Primary", "source": "nvd@nist.gov", "cvssData": {"scope": "UNCHANGED", "version": "3.1", "baseScore": 9.8, "attackVector": "NETWORK", "baseSeverity": "CRITICAL", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H", "integrityImpact": "HIGH", "userInteraction": "NONE", "attackComplexity": "LOW", "availabilityImpact": "HIGH", "privilegesRequired": "NONE", "confidentialityImpact": "HIGH"}, "impactScore": 5.9, "exploitabilityScore": 3.9}], "cvssMetricV40": [{"type": "Secondary", "source": "cna@cloudflare.com", "cvssData": {"Safety": "NOT_DEFINED", "version": "4.0", "Recovery": "NOT_DEFINED", "baseScore": 5.3, "Automatable": "NOT_DEFINED", "attackVector": "NETWORK", "baseSeverity": "MEDIUM", "valueDensity": "NOT_DEFINED", "vectorString": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:L/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:Amber", "exploitMaturity": "NOT_DEFINED", "providerUrgency": "AMBER", "userInteraction": "PASSIVE", "attackComplexity": "LOW", "attackRequirements": "NONE", "privilegesRequired": "NONE", "subIntegrityImpact": "NONE", "vulnIntegrityImpact": "LOW", "integrityRequirement": "NOT_DEFINED", "modifiedAttackVector": "NOT_DEFINED", "subAvailabilityImpact": "NONE", "vulnAvailabilityImpact": "NONE", "availabilityRequirement": "NOT_DEFINED", "modifiedUserInteraction": "NOT_DEFINED", "modifiedAttackComplexity": "NOT_DEFINED", "subConfidentialityImpact": "NONE", "vulnConfidentialityImpact": "NONE", "confidentialityRequirement": "NOT_DEFINED", "modifiedAttackRequirements": "NOT_DEFINED", "modifiedPrivilegesRequired": "NOT_DEFINED", "modifiedSubIntegrityImpact": "NOT_DEFINED", "modifiedVulnIntegrityImpact": "NOT_DEFINED", "vulnerabilityResponseEffort": "NOT_DEFINED", "modifiedSubAvailabilityImpact": "NOT_DEFINED", "modifiedVulnAvailabilityImpact": "NOT_DEFINED", "modifiedSubConfidentialityImpact": "NOT_DEFINED", "modifiedVulnConfidentialityImpact": "NOT_DEFINED"}}]}, "published": "2025-05-01T01:15:54.267", "references": [{"url": "https://github.com/cloudflare/workers-oauth-provider/pull/27", "tags": ["Issue Tracking", "Patch"], "source": "cna@cloudflare.com"}], "vulnStatus": "Analyzed", "weaknesses": [{"type": "Secondary", "source": "cna@cloudflare.com", "description": [{"lang": "en", "value": "CWE-287"}]}, {"type": "Primary", "source": "nvd@nist.gov", "description": [{"lang": "en", "value": "NVD-CWE-noinfo"}]}], "descriptions": [{"lang": "en", "value": "PKCE was implemented in the OAuth implementation in workers-oauth-provider that is part of MCP framework https://github.com/cloudflare/workers-mcp . However, it\u00a0was found that an attacker could cause the check to be skipped.\n\n\nFixed in:\n\n \n\n https://github.com/cloudflare/workers-oauth-provider/pull/27 https://github.com/cloudflare/workers-oauth-provider/pull/27 \n\n\nImpact: \n\nPKCE is a defense-in-depth mechanism against certain kinds of attacks and was an optional extension in OAuth 2.0 which became required in the OAuth 2.1 draft. (Note that the MCP specification requires OAuth 2.1.).\u00a0This bug completely bypasses PKCE protection."}, {"lang": "es", "value": "PKCE se implement\u00f3 en la implementaci\u00f3n de OAuth en workers-oauth-provider, que forma parte del framework MCP (https://github.com/cloudflare/workers-mcp). Sin embargo, se detect\u00f3 que un atacante podr\u00eda omitir la comprobaci\u00f3n. Corregido en: https://github.com/cloudflare/workers-oauth-provider/pull/27 https://github.com/cloudflare/workers-oauth-provider/pull/27 Impacto: PKCE es un mecanismo de defensa en profundidad contra ciertos tipos de ataques y era una extensi\u00f3n opcional en OAuth 2.0, que se convirti\u00f3 en obligatoria en el borrador de OAuth 2.1. (Tenga en cuenta que la especificaci\u00f3n MCP requiere OAuth 2.1). Este error ignora por completo la protecci\u00f3n de PKCE."}], "lastModified": "2025-05-12T19:39:31.053", "configurations": [{"nodes": [{"negate": false, "cpeMatch": [{"criteria": "cpe:2.3:a:cloudflare:workers-oauth-provider:0.0.5:*:*:*:*:*:*:*", "vulnerable": true, "matchCriteriaId": "9B01663B-708A-4C77-9347-EA3AC30A5C94"}], "operator": "OR"}]}], "sourceIdentifier": "cna@cloudflare.com"}

9.8 /10