GHSA-hg3h-g7xc-f7vp

Описание

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:

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

Relevant Code

app/controllers/view_components_system_test_controller.rb:

The route then renders the resolved file:

Exploit Flow

Example request:

Flow:

1. base_path resolves to .../tmp/view_components.
2. The payload resolves to .../tmp/view_components_evil/secret.html.erb.
3. That path is outside the intended temp directory.
4. The string prefix check still passes.
5. 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:

PoC Test

Create test/sandbox/test/system_test_entrypoint_path_traversal_poc_test.rb:

Run:

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:

Or require a separator boundary:

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