critical CVSS 9.9

CVE-2026-41228·PHP vulnerability

Froxlor is open source server administration software. Prior to version 2.3.6, the Froxlor API endpoint `Customers.update` (and `Admins.update`) does not validate the `def_language` parameter against the list of available language files. An authenticated customer can set `def_language` to a path traversal payload (e.g., `../../../../../var/customers/webs/customer1/evil`), which is stored in the database. On subsequent requests, `Language::loadLanguage()` constructs a file path using this value and executes it via `require`, achieving arbitrary PHP code execution as the web server user. Version 2.3.6 fixes the issue.

Severity
critical
Software
PHP
Fixed in
2.3.6
Published
2026-04-23

Affected versions

Until: 2.3.6

Fixed in: 2.3.6

How to fix this CVE

Upgrade Froxlor to version 2.3.6 or later immediately. This release patches a critical API vulnerability in the Customers.update and Admins.update endpoints that allowed authenticated users to inject path traversal payloads into the `def_language` parameter. The flaw enabled arbitrary PHP code execution through unsafe file inclusion. Ensure all PHP-based Froxlor installations are updated to mitigate this remote code execution risk.

sudo dnf update php

Defensia detects this vulnerability

What an exploitation attempt looks like

Sample log line indicative of exploitation attempts:

POST /api/v1/Customers.update|/api/v1/Admins.update.*def_language.*(\.\./|%2e%2e%2f|\.\.\\|%2e%2e%5c)

WAF mitigation (if patching is not yet possible)

Add this rule to your WAF to block exploitation attempts while you schedule the patch. 

Implement a WAF rule to block POST requests to Froxlor API endpoints containing path traversal patterns in the `def_language` parameter. Use a rule that matches regex patterns like (\.\./ or %2e%2e%2f) in the request body and deny with a 403 response. Additionally, enforce strict input validation at the WAF level to only allow alphanumeric language identifiers matching the pattern ^[a-zA-Z0-9_-]+$.

How to check if you are affected

  1. Step 1: Check the installed Froxlor version with: grep -i 'version' /var/www/froxlor/lib/Froxlor/Froxlor.php | head -5
  2. Step 2: Verify if the vulnerable API endpoints are accessible by checking access logs for POST requests to /api/v1/Customers.update or /api/v1/Admins.update patterns
  3. Step 3: Search application logs for suspicious `def_language` parameter values containing path traversal sequences (../ or encoded variants) using: grep -r 'def_language.*\.\./' /var/log/
  4. Step 4: Confirm the patch by verifying Froxlor version is 2.3.6 or later: curl -s http://localhost/admin/index.php | grep -i 'froxlor' | head -1

FAQ

What is CVE-2026-41228?

CVE-2026-41228 is a critical remote code execution vulnerability in Froxlor's API that permits authenticated users to bypass language file validation and execute arbitrary PHP code via path traversal injection in the `def_language` parameter of the Customers.update and Admins.update endpoints.

Is CVE-2026-41228 being actively exploited?

No, CVE-2026-41228 is not currently listed on the CISA Known Exploited Vulnerabilities catalog, and no public exploits have been publicly disclosed. However, the vulnerability is critical and should be patched immediately.

What versions of PHP are affected by CVE-2026-41228?

CVE-2026-41228 affects Froxlor versions prior to 2.3.6. All installations running Froxlor before version 2.3.6 are vulnerable, regardless of the underlying PHP version.

How do I check if my server is vulnerable to CVE-2026-41228?

Check your Froxlor version by running: grep -oP 'VERSION\s*=\s*['\'']\K[^'\'']+' /var/www/froxlor/lib/Froxlor/Froxlor.php — if the version is below 2.3.6, your installation is vulnerable.

Does Defensia detect CVE-2026-41228?

Yes — Defensia's CVE advisory scanner compares installed package versions against the NVD database. If Froxlor is installed on a monitored server, CVE-2026-41228 will appear in your dashboard with remediation steps.

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References

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