CVE-2026-33715: Chamilo LMS has Unauthenticated SSRF and Open Email Relay via install.ajax.php test_mailer action
Chamilo LMS is an open-source learning management system. In version 2.0-RC.2, the file public/main/inc/ajax/install.ajax.php is accessible without authentication on fully installed instances because, unlike other AJAX endpoints, it does not include the global.inc.php file that performs authentication and installation-completed checks. Its testmailer action accepts an arbitrary Symfony Mailer DSN string from POST data and uses it to connect to an attacker-specified SMTP server, enabling Server-Side Request Forgery (SSRF) into internal networks via the SMTP protocol. An unauthenticated attacker can also abuse this to weaponize the Chamilo server as an open email relay for phishing and spam campaigns, with emails appearing to originate from the server's IP address. Additionally, error responses from failed SMTP connections may disclose information about internal network topology and running services. This issue has been fixed in version 2.0.0-RC.3.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
Chamilo LMSto a version that resolves this vulnerability.Fixed in 2.0.0-RC.3 - Configuration
Update Chamilo so that the install.ajax.php test_mailer action is not accessible without authentication on fully installed instances (so unauthenticated attackers cannot abuse it for SMTP/SSRF and open relay behavior).
Chamilo LMS (public/main/inc/ajax/install.ajax.php) Authentication/installation-completed checks (global.inc.php inclusion) = Ensure the endpoint includes global.inc.php so it requires authentication and verifies installation completion - Compensating control
Restrict or firewall outbound SMTP connectivity from the Chamilo server so it cannot connect to attacker-specified internal/external SMTP servers (mitigates SSRF via the SMTP protocol).
Event History
Frequently Asked Questions
What is the severity of CVE-2026-33715?
CVE-2026-33715 is considered a medium severity vulnerability due to its potential for unauthorized access and exploitation.
How do I fix CVE-2026-33715?
To fix CVE-2026-33715, upgrade Chamilo LMS to version 2.0.0-RC.3 or later where the vulnerability has been addressed.
What kind of exploitation does CVE-2026-33715 allow?
CVE-2026-33715 allows for unauthenticated Server-Side Request Forgery (SSRF) and open email relay, which can be exploited by attackers.
Which version of Chamilo LMS is affected by CVE-2026-33715?
Chamilo LMS versions prior to 2.0.0-RC.3 are affected by CVE-2026-33715.
Is authentication required to exploit CVE-2026-33715?
No, CVE-2026-33715 can be exploited without authentication, making it a critical security concern.