high CVSS 7.1

CVE-2026-33704·PHP vulnerability

Chamilo LMS is a learning management system. Prior to 1.11.38, any authenticated user (including students) can write arbitrary content to files on the server via the BigUpload endpoint. The key parameter controls the filename and the raw POST body becomes the file content. While .php extensions are filtered to .phps, the .pht extension passes through unmodified. On Apache configurations where .pht is handled as PHP, this leads to Remote Code Execution. This vulnerability is fixed in 1.11.38.

Severity
high
Software
PHP
Fixed in
1.11.38
Published
2026-04-10

Affected versions

Until: 1.11.38

Fixed in: 1.11.38

How to fix this CVE

Upgrade Chamilo LMS to version 1.11.38 or later to patch the arbitrary file write vulnerability in the BigUpload endpoint. This update restricts dangerous file extensions beyond just .php, preventing attackers from uploading executable files with alternative extensions like .pht. Organizations running older versions should prioritize this update as the vulnerability allows authenticated users to execute arbitrary code on the server.

sudo dnf update php

Defensia detects this vulnerability

What an exploitation attempt looks like

Sample log line indicative of exploitation attempts:

POST /main/upload/bigupload.php.*key=.*\.pht|POST.*BigUpload.*Content-Disposition.*filename.*\.pht

WAF mitigation (if patching is not yet possible)

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

Block POST requests to BigUpload endpoints with filename parameters containing .pht, .phtml, .php3, .php4, .php5 extensions. Implement strict file extension whitelisting that only permits safe file types (images, documents) and rejects all executable script extensions regardless of case variation.

How to check if you are affected

  1. Step 1: Check your Chamilo LMS version by examining the version file: cat /path/to/chamilo/main/inc/conf/version.php | grep version_name
  2. Step 2: Verify if the BigUpload endpoint is accessible by checking if /main/upload/bigupload.php exists and is callable by authenticated users
  3. Step 3: Review Apache configuration to confirm if .pht files are processed as PHP: grep -r 'AddType.*pht' /etc/apache2/
  4. Step 4: Confirm the patch by checking if file extension validation in BigUpload now blocks .pht uploads or renames them to .phts

FAQ

What is CVE-2026-33704?

This is a file upload vulnerability in Chamilo LMS's BigUpload endpoint that allows authenticated users to write arbitrary files to the server by bypassing PHP extension filters. On Apache servers configured to execute .pht files as PHP, attackers can achieve remote code execution.

Is CVE-2026-33704 being actively exploited?

No, this vulnerability is not currently listed in the CISA Known Exploited Vulnerabilities catalog and no public exploits are widely available, though the attack method is straightforward for authenticated users.

What versions of Chamilo LMS are affected by CVE-2026-33704?

All versions prior to 1.11.38 are vulnerable. The fix was released in version 1.11.38 and should be applied immediately.

How do I check if my server is vulnerable to CVE-2026-33704?

Run: cat /path/to/chamilo/main/inc/conf/version.php | grep version_name and verify if the version is below 1.11.38. Additionally, check if .pht file uploads are blocked by attempting to upload a test file with that extension.

Does Defensia detect CVE-2026-33704?

Yes — Defensia's CVE advisory scanner compares installed package versions against the NVD database. If Chamilo LMS is installed on a monitored server, CVE-2026-33704 will appear in your dashboard with remediation steps.

Related PHP CVEs

CVE-2026-39337CVSS 10ChurchCRM is an open-source church management system. Prior to 7.1.0, critical pre-authentication remote code execution vulnerability in ChurchCRM's setup wizard allows unauthenticated attackers to inject arbitrary PHP code during the initial installation process, leading to complete server compromise. The "$dbPassword" variable is not sanitized. This vulnerability exists due to an incomplete fix for CVE-2025-62521. This vulnerability is fixed in 7.1.0.
CVE-2024-5932CVSS 10The GiveWP – Donation Plugin and Fundraising Platform plugin for WordPress is vulnerable to PHP Object Injection in all versions up to, and including, 3.14.1 via deserialization of untrusted input from the 'give_title' parameter. This makes it possible for unauthenticated attackers to inject a PHP Object. The additional presence of a POP chain allows attackers to execute code remotely, and to delete arbitrary files.
CVE-2026-28289CVSS 10FreeScout is a free help desk and shared inbox built with PHP's Laravel framework. A patch bypass vulnerability for CVE-2026-27636 in FreeScout 1.8.206 and earlier allows any authenticated user with file upload permissions to achieve Remote Code Execution (RCE) on the server by uploading a malicious .htaccess file using a zero-width space character prefix to bypass the security check. The vulnerability exists in the sanitizeUploadedFileName() function in app/Http/Helper.php. The function contains a Time-of-Check to Time-of-Use (TOCTOU) flaw where the dot-prefix check occurs before sanitization removes invisible characters. This vulnerability is fixed in 1.8.207.
CVE-2025-62521CVSS 10ChurchCRM is an open-source church management system. Prior to version 5.21.0, a pre-authentication remote code execution vulnerability in ChurchCRM's setup wizard allows unauthenticated attackers to inject arbitrary PHP code during the initial installation process, leading to complete server compromise. The vulnerability exists in `setup/routes/setup.php` where user input from the setup form is directly concatenated into a PHP configuration template without any validation or sanitization. Any parameter in the setup form can be used to inject PHP code that gets written to `Include/Config.php`, which is then executed on every page load. This is more severe than typical authenticated RCE vulnerabilities because it requires no credentials and affects the installation process that administrators must complete. Version 5.21.0 patches the issue.
CVE-2025-47916CVSS 10Invision Community 5.0.0 before 5.0.7 allows remote code execution via crafted template strings to themeeditor.php. The issue lies within the themeeditor controller (file: /applications/core/modules/front/system/themeeditor.php), where a protected method named customCss can be invoked by unauthenticated users. This method passes the value of the content parameter to the Theme::makeProcessFunction() method; hence it is evaluated by the template engine. Accordingly, this can be exploited by unauthenticated attackers to inject and execute arbitrary PHP code by providing crafted template strings.

References

Track CVEs across your fleet automatically

Defensia scans your Linux servers and tells you exactly which ones are running vulnerable versions — including CVE-2026-33704. Free for 1 server.

Get started free