critical CVSS 9.8

CVE-2026-33698·PHP vulnerability

Chamilo LMS is a learning management system. Prior to 1.11.38, a chained attack can enable otherwise-blocked PHP code from the main/install/ directory and allow an unauthenticated attacker to modify existing files or create new files where allowed by system permissions. This only affects portals with the main/install/ directory still present and read-accessible. This vulnerability is fixed in 1.11.38.

Severity
critical
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

Organizations running Chamilo LMS must upgrade to version 1.11.38 or later immediately to patch this critical remote code execution vulnerability. If the main/install/ directory is still present on your server, remove or restrict access to it via web server configuration. Verify that your PHP installation and Chamilo LMS deployment are fully updated and that installation directories are not web-accessible.

sudo dnf update php && sudo systemctl restart httpd

Defensia detects this vulnerability

What an exploitation attempt looks like

Sample log line indicative of exploitation attempts:

POST|GET /main/install/ HTTP/1.1.*User-Agent:.*Accept.*Content-Type:.*php|php5|php7

WAF mitigation (if patching is not yet possible)

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

Block all HTTP requests to /main/install/ directory with a 403 Forbidden response. Implement location-based rules: if request_uri ~ '^/main/install/' { return 403; } in nginx or <Directory /main/install> Deny from all </Directory> in Apache httpd.conf

How to check if you are affected

  1. Run `php -v` to verify your current PHP version and confirm if Chamilo LMS is installed
  2. Check if the main/install/ directory exists: `ls -la /path/to/chamilo/main/install/` (note the presence and permissions)
  3. Search web server access logs for requests to /main/install/ using: `grep -i 'main/install' /var/log/apache2/access.log /var/log/nginx/access.log 2>/dev/null`
  4. Verify Chamilo LMS version by checking the version file: `grep -i version /path/to/chamilo/main/inc/conf/version.php` and confirm it is 1.11.38 or later

Indicators of compromise

  • /main/install/
  • /main/install/index.php
  • /main/install/install.php
  • chamilo_install_detected

FAQ

What is CVE-2026-33698?

This is a critical vulnerability in Chamilo LMS that allows unauthenticated attackers to bypass access controls and execute arbitrary PHP code through the installation directory if it remains accessible after setup. The vulnerability can lead to unauthorized file modification, creation, and complete system compromise.

Is CVE-2026-33698 being actively exploited?

No, this vulnerability is not currently listed on the CISA Known Exploited Vulnerabilities (KEV) catalog, and no public exploits have been released. However, given its critical severity and ease of exploitation, organizations should prioritize patching immediately.

What versions of Chamilo LMS are affected by CVE-2026-33698?

All versions of Chamilo LMS prior to 1.11.38 are affected. The vulnerability only impacts installations where the main/install/ directory remains present and is readable by the web server.

How do I check if my server is vulnerable to CVE-2026-33698?

Run `test -d /path/to/chamilo/main/install/ && echo 'Vulnerable - install directory present' || echo 'Not vulnerable - install directory removed'` and verify your Chamilo version with `grep version /path/to/chamilo/main/inc/conf/version.php`

Does Defensia detect CVE-2026-33698?

Yes — Defensia's CVE advisory scanner compares installed package versions against the NVD database. If Chamilo LMS is installed on a monitored server, CVE-2026-33698 will appear in your dashboard with remediation steps.

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References

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