view_component: System Test Entry Point Path Check Allows Sibling Directory Escape

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

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

EPSS

• CVE-2026-44837: 0.41% estimated exploitation activity in the next 30 days; percentile 35.50 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

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/viewcomponentssystemtestcontroller.rb: The route then renders the resolved file: Exploit Flow Example request: Flow: 1. basepath resolves to .../tmp/viewcomponents. 2. The payload resolves to .../tmp/viewcomponentsevil/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…

Published by the source

8 May 2026, 23:33 UTC

Last modified by the source

8 Jun 2026, 23:34 UTC

Source last checked

26 Oct 2026, 15:52 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-hg3h-g7xc-f7vp

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# Patch Next advisory brief: CVE-2026-44837

Advisory: view_component: System Test Entry Point Path Check Allows Sibling Directory Escape
IDs: CVE-2026-44837, GHSA-hg3h-g7xc-f7vp
Record: https://patchnext.com/advisories/cve-2026-44837 (revision 1, source checked 26 Oct 2026, 15:52 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 5.9)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: view_component 4.9.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- RubyGems view_component: affected >= 3.0.0, < 4.9.0; fixed in 4.9.0

## Suggested inspection (read-only)
- RubyGems view_component: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on view_component.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-hg3h-g7xc-f7vp (GitHub-reviewed advisory GHSA-hg3h-g7xc-f7vp lists affected ranges: RubyGems view_component >=3.0.0 <4.9.0)

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