CVE-2026-30882: Chamilo LMS Reflected XSS Vulnerability

CVE-2026-30882 Overview

CVE-2026-30882 is a reflected Cross-Site Scripting (XSS) vulnerability in Chamilo LMS, an open-source learning management system. The flaw affects Chamilo LMS version 1.11.34 and prior. The session category listing page echoes the keyword parameter from $_REQUEST directly into an HTML href attribute without encoding or sanitization. An attacker can break out of the attribute context and inject arbitrary HTML or JavaScript. The vulnerability triggers when pagination controls render, which occurs when session categories exceed the 20-item page limit. The issue is patched in version 1.11.36 [CWE-79].

Critical Impact

A successful exploit can execute attacker-controlled JavaScript in the authenticated administrator's browser, enabling session theft, unauthorized actions, and content modification within the Chamilo LMS interface.

Affected Products

• Chamilo LMS 1.11.34 and prior
• Chamilo LMS session category listing component
• Installations with more than 20 session categories (required for pagination to render)

Discovery Timeline

• 2026-03-16 - CVE-2026-30882 published to NVD
• 2026-03-17 - Last updated in NVD database

Technical Details for CVE-2026-30882

Vulnerability Analysis

The vulnerability resides in the session category listing page of Chamilo LMS. The application retrieves the keyword parameter from $_REQUEST and reflects it into a pagination link's href attribute. Because the application performs no output encoding or input sanitization, an attacker can supply a payload that closes the attribute and injects new HTML elements or JavaScript handlers.

The injection point is conditional on page rendering logic. The pagination controls render only when the number of session categories exceeds the page limit of 20. Without this condition, the vulnerable code path is not reached. Exploitation requires user interaction, typically by enticing an authenticated user to click a crafted link.

Successful exploitation runs JavaScript in the victim's browser within the Chamilo LMS origin. An attacker can read session cookies that are not HttpOnly, perform administrative actions on behalf of the victim, or modify rendered content to facilitate further attacks [CWE-79].

Root Cause

The root cause is improper neutralization of input during web page generation. User-controlled input from $_REQUEST['keyword'] is concatenated into an HTML attribute without applying htmlspecialchars() or an equivalent context-aware encoder. The pagination link construction trusts the raw parameter value, allowing attribute-context breakout using "> followed by arbitrary markup.

Attack Vector

The attack vector is network-based and requires user interaction. An attacker crafts a URL targeting the session category listing endpoint with a malicious keyword value. The payload uses "> to terminate the existing href attribute, followed by an injected event handler or <script> element. The victim must visit the URL on an instance where more than 20 session categories exist. When pagination renders, the browser executes the injected payload in the Chamilo LMS context.

The vulnerability mechanism is described in the GitHub Security Advisory GHSA-qg5f-gq95-9vhq. No public proof-of-concept exploit code is available at this time.

Detection Methods for CVE-2026-30882

Indicators of Compromise

• HTTP requests to Chamilo LMS session category endpoints containing keyword parameter values with ">, <script, onerror=, onload=, or javascript: substrings
• Web server access logs showing URL-encoded XSS payloads (for example, %22%3E%3Cscript%3E) in query strings targeting session category pages
• Unexpected outbound requests from administrator browsers to attacker-controlled domains immediately after accessing Chamilo LMS
• Anomalous session activity, including new administrative actions originating from legitimate accounts following a crafted link click

Detection Strategies

• Deploy web application firewall (WAF) rules to inspect query string parameters for HTML attribute breakout patterns on Chamilo LMS endpoints
• Review application access logs for requests targeting the session category listing page with suspicious keyword parameter content
• Correlate browser telemetry on administrator endpoints with Chamilo LMS page loads to identify script execution anomalies

Monitoring Recommendations

• Enable verbose HTTP logging on the Chamilo LMS web tier and forward logs to a centralized analytics platform for retention and search
• Alert on outbound DNS or HTTP requests from administrator workstations to newly registered or low-reputation domains following LMS access
• Track the Chamilo LMS version in inventory tooling and flag any instance running 1.11.34 or earlier for remediation

How to Mitigate CVE-2026-30882

Immediate Actions Required

• Upgrade Chamilo LMS to version 1.11.36 or later, as published in the GitHub Release v1.11.36
• Restrict access to the Chamilo LMS administrative interface using network controls or VPN until the patch is applied
• Communicate with administrators to avoid clicking untrusted links that target Chamilo LMS URLs
• Review web server logs for prior exploitation attempts against the session category listing endpoint

Patch Information

The vendor fixed the vulnerability in Chamilo LMS version 1.11.36. The patch applies output encoding to the keyword parameter before it is rendered into the pagination link's href attribute. Patch details are documented in the GitHub Security Advisory GHSA-qg5f-gq95-9vhq and the GitHub Release v1.11.36.

Workarounds

• Deploy WAF rules that block requests containing attribute-breakout sequences such as "><, " onerror=, or " onload= in the keyword parameter
• Set the HttpOnly and Secure flags on Chamilo LMS session cookies to limit cookie theft impact from XSS execution
• Enforce a strict Content Security Policy (CSP) that disallows inline scripts and restricts script sources to trusted origins
• Limit administrative access to trusted networks and require multi-factor authentication for privileged accounts

# Example Content Security Policy header to limit XSS impact
add_header Content-Security-Policy "default-src 'self'; script-src 'self'; object-src 'none'; base-uri 'self'; frame-ancestors 'self';";
add_header X-XSS-Protection "1; mode=block";
add_header X-Content-Type-Options "nosniff";