CVE-2026-34161
Chamilo LMS: Stored XSS via Malicious File Upload in Social Post Attachments Leads to Arbitrary JavaScript Execution
Description
Chamilo LMS is an open-source learning management system. In versions prior to 2.0.0-RC.3, a Stored Cross-Site Scripting (XSS) vulnerability exists in the social post attachment upload functionality, where an authenticated user can upload a malicious HTML file containing JavaScript via the /api/social_post_attachments endpoint. The uploaded file is served back from the application at the generated contentUrl without sanitization, content type restrictions, or a Content-Disposition: attachment header, causing the JavaScript to execute in the browser within the application's origin. Because the payload is stored server-side and runs in the trusted origin, an attacker can perform session hijacking, account takeover, privilege escalation (if an admin views the link), and arbitrary actions on behalf of the victim. This issue has been fixed in version 2.0.0-RC.3.
INFO
Published Date :
April 14, 2026, 9:16 p.m.
Last Modified :
July 24, 2026, 10:10 p.m.
Remotely Exploit :
Yes !
Source :
[email protected]
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS | 134c704f-9b21-4f2e-91b3-4a467353bcc0 | |||||
| CVSS 3.1 | MEDIUM | [email protected] | ||||
| CVSS 4.0 | MEDIUM | [email protected] |
Solution
- Update Chamilo LMS to version 2.0.0-RC.3.
- Apply security patches for older versions.
- Sanitize user-uploaded files.
- Implement content type restrictions.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-34161.
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-34161 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-34161
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-34161 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-34161 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
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CVE Translated by [email protected]
Jul. 24, 2026
Action Type Old Value New Value Added Translation Title: Chamilo LMS de Chamilo, Description: Chamilo LMS es un sistema de gestión de aprendizaje de código abierto. En versiones anteriores a la 2.0.0-RC.3, existe una vulnerabilidad de cross-site scripting (XSS) almacenado en la funcionalidad de carga de archivos adjuntos de publicaciones sociales, donde un usuario autenticado puede cargar un archivo HTML malicioso que contiene JavaScript a través del endpoint /API/social_post_attachments. El archivo cargado es servido de vuelta desde la aplicación en la contentUrl generada sin saneamiento, restricciones de tipo de contenido, o una cabecera Content-Disposition: attachment, lo que provoca que el JavaScript se ejecute en el navegador dentro del origen de la aplicación. Debido a que la carga útil se almacena en el lado del servidor y se ejecuta en el origen de confianza, un atacante puede realizar secuestro de sesión, toma de control de cuenta, escalada de privilegios (si un administrador ve el enlace), y acciones arbitrarias en nombre de la víctima. Este problema ha sido solucionado en la versión 2.0.0-RC.3. -
CVE Modified by [email protected]
Jun. 17, 2026
Action Type Old Value New Value Added Affected [{'vendor': 'chamilo', 'product': 'chamilo-lms', 'versions': [{'status': 'affected', 'version': '< 2.0.0-RC.3'}]}] -
CVE Modified by 134c704f-9b21-4f2e-91b3-4a467353bcc0
Jun. 17, 2026
Action Type Old Value New Value Added SSVC {'id': 'CVE-2026-34161', 'role': 'CISA Coordinator', 'options': [{'exploitation': 'none'}, {'automatable': 'no'}, {'technicalImpact': 'partial'}], 'version': '2.0.3', 'timestamp': '2026-04-16T13:49:14.409455Z'} -
Initial Analysis by [email protected]
Apr. 23, 2026
Action Type Old Value New Value Added CVSS V3.1 AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N Added CPE Configuration OR *cpe:2.3:a:chamilo:chamilo_lms:2.0.0:alpha1:*:*:*:*:*:* *cpe:2.3:a:chamilo:chamilo_lms:2.0.0:alpha2:*:*:*:*:*:* *cpe:2.3:a:chamilo:chamilo_lms:2.0.0:alpha3:*:*:*:*:*:* *cpe:2.3:a:chamilo:chamilo_lms:2.0.0:alpha4:*:*:*:*:*:* *cpe:2.3:a:chamilo:chamilo_lms:2.0.0:alpha5:*:*:*:*:*:* *cpe:2.3:a:chamilo:chamilo_lms:2.0.0:beta1:*:*:*:*:*:* *cpe:2.3:a:chamilo:chamilo_lms:2.0.0:beta2:*:*:*:*:*:* *cpe:2.3:a:chamilo:chamilo_lms:2.0.0:beta3:*:*:*:*:*:* *cpe:2.3:a:chamilo:chamilo_lms:2.0.0:rc1:*:*:*:*:*:* *cpe:2.3:a:chamilo:chamilo_lms:2.0.0:rc2:*:*:*:*:*:* *cpe:2.3:a:chamilo:chamilo_lms:*:*:*:*:*:*:*:* versions up to (including) 1.11.38 Added Reference Type GitHub, Inc.: https://github.com/chamilo/chamilo-lms/commit/7c4965e48769d1d06413836429e386816a465c7f Types: Patch Added Reference Type GitHub, Inc.: https://github.com/chamilo/chamilo-lms/commit/da671d66a146887be3a16eabc5dcf0a92c55f7da Types: Patch Added Reference Type GitHub, Inc.: https://github.com/chamilo/chamilo-lms/releases/tag/v2.0.0-RC.3 Types: Product, Release Notes Added Reference Type GitHub, Inc.: https://github.com/chamilo/chamilo-lms/security/advisories/GHSA-273p-jw9w-3g22 Types: Vendor Advisory -
New CVE Received by [email protected]
Apr. 14, 2026
Action Type Old Value New Value Added Description Chamilo LMS is an open-source learning management system. In versions prior to 2.0.0-RC.3, a Stored Cross-Site Scripting (XSS) vulnerability exists in the social post attachment upload functionality, where an authenticated user can upload a malicious HTML file containing JavaScript via the /api/social_post_attachments endpoint. The uploaded file is served back from the application at the generated contentUrl without sanitization, content type restrictions, or a Content-Disposition: attachment header, causing the JavaScript to execute in the browser within the application's origin. Because the payload is stored server-side and runs in the trusted origin, an attacker can perform session hijacking, account takeover, privilege escalation (if an admin views the link), and arbitrary actions on behalf of the victim. This issue has been fixed in version 2.0.0-RC.3. Added CVSS V4.0 AV:N/AC:L/AT:N/PR:L/UI:P/VC:L/VI:L/VA:N/SC:L/SI:L/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X Added CWE CWE-79 Added Reference https://github.com/chamilo/chamilo-lms/commit/7c4965e48769d1d06413836429e386816a465c7f Added Reference https://github.com/chamilo/chamilo-lms/commit/da671d66a146887be3a16eabc5dcf0a92c55f7da Added Reference https://github.com/chamilo/chamilo-lms/releases/tag/v2.0.0-RC.3 Added Reference https://github.com/chamilo/chamilo-lms/security/advisories/GHSA-273p-jw9w-3g22