CI4MS Theme::upload is vulnerable to Zip Slip leading to RCE

Exploitation

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

CVSS 4.0

9.4 · CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H · score source

EPSS

• CVE-2026-41203: 0.62% estimated exploitation activity in the next 30 days; percentile 49.75 (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 ci4ms Theme::upload extracts user uploaded ZIP archives without validating entry names, allowing an authenticated backend user with the theme create permission to write files to arbitrary filesystem locations (Zip Slip) and achieve remote code execution by dropping a PHP file under the public web root. Details modules/Theme/Controllers/Theme.php:13-56 implements the theme upload action. ZipArchive::extractTo() is called directly with no iteration over entry names to verify they resolve inside the destination: A ZIP containing entries like ../../public/shell.php is extracted outside writable/tmp/ into directories served by PHP. The author validates entries correctly in modules/Methods/Controllers/Methods.php:165-175 with a realpath + regex loop; the same check is missing here. Routing: modules/Theme/Config/Routes.php binds POST backend/themes/themesUpload to Theme::upload with role=create. Although ThemeConfig itself does not list the route in csrfExcept, the upload handler is…

Published by the source

22 Apr 2026, 17:29 UTC

Last modified by the source

8 May 2026, 19:55 UTC

Source last checked

26 Oct 2026, 14:40 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-xv3r-vr59-95rg

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# Patch Next advisory brief: CVE-2026-41203

Advisory: CI4MS Theme::upload is vulnerable to Zip Slip leading to RCE
IDs: CVE-2026-41203, GHSA-xv3r-vr59-95rg
Record: https://patchnext.com/advisories/cve-2026-41203 (revision 1, source checked 26 Oct 2026, 14:40 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Critical (CVSS 9.4)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: ci4-cms-erp/ci4ms 0.31.5.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- Packagist ci4-cms-erp/ci4ms: affected < 0.31.5.0; fixed in 0.31.5.0

## Suggested inspection (read-only)
- Packagist ci4-cms-erp/ci4ms: 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 ci4-cms-erp/ci4ms.
- 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-xv3r-vr59-95rg (GitHub-reviewed advisory GHSA-xv3r-vr59-95rg lists affected ranges: Packagist ci4-cms-erp/ci4ms >=0 <0.31.5.0)

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