CVE-2025-4143
6.1 · MEDIUMOverview
CVE-2025-4143 is a medium-severity vulnerability affecting cloudflare workers-oauth-provider. It was published on May 1, 2025 and has a CVSS 3.1 base score of 6.1 (MEDIUM).
This vulnerability has a CVSS 3.1 base score of 6.1, rated MEDIUM. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.
Technical Description
The OAuth implementation in workers-oauth-provider that is part of MCP framework https://github.com/cloudflare/workers-mcp , did not correctly validate that redirect_uri was on the allowed list of redirect URIs for the given client registration.
Fixed in: https://github.com/cloudflare/workers-oauth-provider/pull/26 https://github.com/cloudflare/workers-oauth-provider/pull/26
Impact:
Under certain circumstances (see below), if a victim had previously authorized with a server built on workers-oath-provider, and an attacker could later trick the victim into visiting a malicious web site, then attacker could potentially steal the victim's credentials to the same OAuth server and subsequently impersonate them.
In order for the attack to be possible, the OAuth server's authorized callback must be designed to auto-approve authorizations that appear to come from an OAuth client that the victim has authorized previously. The authorization flow is not implemented by workers-oauth-provi
Remediation
Check the references section for vendor advisories and patches from cloudflare. Update workers-oauth-provider to the latest patched version. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.
Affected Products
| Vendor | Product | Versions | Status |
|---|
Frequently Asked Questions
What is CVE-2025-4143?
CVE-2025-4143 is a medium-severity vulnerability affecting cloudflare workers-oauth-provider. It was published on May 1, 2025 and has a CVSS 3.1 base score of 6.1 (MEDIUM).
How severe is CVE-2025-4143?
This vulnerability has a CVSS 3.1 base score of 6.1, rated MEDIUM. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.
How do I fix or remediate CVE-2025-4143?
Check the references section for vendor advisories and patches from cloudflare. Update workers-oauth-provider to the latest patched version. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.
How can CyberStrike help with CVE-2025-4143?
CyberStrike's AI-powered security agents can automatically detect CVE-2025-4143 across your infrastructure using autonomous pentesting, DAST scanning, and HackBrowser. The platform continuously monitors for known vulnerabilities and provides actionable remediation guidance prioritized by real-world exploitability.
How CyberStrike Helps
AI agents map your attack surface to find vulnerabilities like this one.
Automated penetration testing that runs continuously, not just quarterly.
AI-driven PR review catches vulnerable dependencies before they ship.
Browser-based exploitation validates findings with real proof-of-concept.
Related MEDIUM CVEs from 2025
View all →OpenID Connect Core through 1.0 errata set 2 allows audience injection in certain situations. When t
In certain IETF OAuth 2.0-related specifications, when the JSON Web Token Profile for OAuth 2.0 Clie
Missing Critical Step in Authentication vulnerability in Elfatek Elektronics ANKA JPD-00028 allows A
In version v0.3.8 of open-webui/open-webui, sensitive actions such as deleting and resetting are per
Parse Server is an open source backend that can be deployed to any infrastructure that can run Node.
Dell Client Platform BIOS contains a Stack-based Buffer Overflow Vulnerability. A high privileged at
In JetBrains Toolbox App before 2.6 unencrypted credential transmission during SSH authentication wa
VMware NSX contains a stored Cross-Site Scripting (XSS) vulnerability in the gateway firewall due to
Authentication vulnerability in the distributed collaboration framework module Impact: Successful ex
SAPCAR allows an attacker logged in with high privileges to create a malicious SAR archive in SAPCAR
SAPCAR allows an attacker logged in with high privileges to override the permissions of the current
DSpace open source software is a repository application which provides durable access to digital res