GHSA-QGP8-V765-QXX9

Vulnerability from github – Published: 2025-05-01 17:01 – Updated: 2025-05-01 17:01
VLAI?
Summary
@cloudflare/workers-oauth-provider PKCE bypass via downgrade attack
Details

Summary

PKCE was implemented in the OAuth implementation in workers-oauth-provider that is part of MCP framework. However, it was found that an attacker could cause the check to be skipped.

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.

Patches

Fixed in: https://github.com/cloudflare/workers-oauth-provider/pull/27

We patched up the vulnerabilities in the latest version, v 0.0.5 of the Workers OAuth provider (https://www.npmjs.com/package/@cloudflare/workers-oauth-provider). You'll need to update your MCP servers to use that version to resolve the vulnerability.

Workarounds

None

Severity ?
5.3 (Medium)
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
Show details on source website
To clipboard 

{
  "affected": [
    {
      "package": {
        "ecosystem": "npm",
        "name": "@cloudflare/workers-oauth-provider"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "0.0.5"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2025-4144"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-287"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2025-05-01T17:01:42Z",
    "nvd_published_at": null,
    "severity": "MODERATE"
  },
  "details": "### Summary\nPKCE 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.\n\n### Impact\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.)\nThis bug completely bypasses PKCE protection.\n\n\n### Patches\nFixed in: https://github.com/cloudflare/workers-oauth-provider/pull/27\n\nWe patched up the vulnerabilities in the latest version, v 0.0.5 of the Workers OAuth provider (https://www.npmjs.com/package/@cloudflare/workers-oauth-provider). You\u0027ll need to update your MCP servers to use that version to resolve the vulnerability.\n\n### Workarounds\nNone",
  "id": "GHSA-qgp8-v765-qxx9",
  "modified": "2025-05-01T17:01:42Z",
  "published": "2025-05-01T17:01:42Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/cloudflare/workers-oauth-provider/security/advisories/GHSA-qgp8-v765-qxx9"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2025-4144"
    },
    {
      "type": "WEB",
      "url": "https://github.com/cloudflare/workers-oauth-provider/pull/27"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/cloudflare/workers-oauth-provider"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "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",
      "type": "CVSS_V4"
    }
  ],
  "summary": "@cloudflare/workers-oauth-provider PKCE bypass via downgrade attack"
}


Log in or create an account to share your comment.




Tags
Taxonomy of the tags.




Sightings

Author Source Type Date

Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.



Detection rules are retrieved from Rulezet.