CVE-2026-5468: Casbin Casdoor XSS Vulnerability

CVE-2026-5468 Overview

A Cross-Site Scripting (XSS) vulnerability has been discovered in Casdoor version 2.356.0, an open-source Identity and Access Management (IAM) platform developed by Casbin. This security flaw affects the dangerouslySetInnerHTML function, which is commonly used in React applications to inject raw HTML into the DOM. The vulnerability can be exploited through manipulation of the formCss, formCssMobile, or formSideHtml arguments, allowing attackers to inject malicious scripts that execute in the context of other users' browsers.

The attack can be initiated remotely over the network and requires low privileges with some user interaction. A public exploit has been disclosed, increasing the risk of active exploitation attempts.

Critical Impact

Successful exploitation allows attackers to execute arbitrary JavaScript in victims' browsers, potentially leading to session hijacking, credential theft, defacement, or further attacks against authenticated users of the Casdoor platform.

Affected Products

• Casbin Casdoor version 2.356.0

Discovery Timeline

• 2026-04-03 - CVE-2026-5468 published to NVD
• 2026-04-09 - Last updated in NVD database

Technical Details for CVE-2026-5468

Vulnerability Analysis

This vulnerability is classified as CWE-79 (Improper Neutralization of Input During Web Page Generation), commonly known as Cross-Site Scripting. The flaw exists in Casdoor's form customization functionality, where user-supplied input is passed directly to React's dangerouslySetInnerHTML function without proper sanitization.

The dangerouslySetInnerHTML property in React is explicitly named to warn developers of its security implications—it renders raw HTML content directly into the DOM, bypassing React's built-in XSS protections. When untrusted input from the formCss, formCssMobile, or formSideHtml parameters flows into this function without adequate input validation or output encoding, attackers can inject malicious HTML containing JavaScript payloads.

The vendor was contacted early about this disclosure but did not respond, leaving users without an official patch at the time of publication.

Root Cause

The root cause of this vulnerability is insufficient input sanitization before rendering user-controlled content through the dangerouslySetInnerHTML React property. The application fails to properly validate, sanitize, or encode the HTML/CSS content supplied via the formCss, formCssMobile, and formSideHtml parameters before inserting them into the rendered page. This allows attackers to embed script tags or event handlers (such as onerror, onload) within the injected content, which execute when the page renders in a victim's browser.

Attack Vector

The attack is network-based and requires an authenticated user with low privileges to inject malicious content into the form customization fields. Once the malicious payload is stored, any user viewing the affected form will have the malicious script execute in their browser context.

An attacker could craft a malicious payload containing JavaScript within the formCss or formSideHtml parameters. For example, injecting an HTML element with an inline event handler such as <img src=x onerror="malicious_script()"> or a <script> tag directly would result in code execution when the form is rendered. The injected script runs with the privileges of the viewing user, potentially allowing session token theft, keylogging, or redirection to phishing sites.

For detailed technical information about this vulnerability, refer to the VulDB Vulnerability Entry.

Detection Methods for CVE-2026-5468

Indicators of Compromise

• Unexpected JavaScript code or script tags present in form customization fields (formCss, formCssMobile, formSideHtml)
• Suspicious HTML elements containing event handlers (e.g., onerror, onload, onclick) in stored form configurations
• Abnormal outbound network connections from client browsers after accessing Casdoor login or registration forms
• User reports of unexpected redirects or browser behavior when accessing the Casdoor platform

Detection Strategies

• Implement Web Application Firewall (WAF) rules to detect and block XSS payloads in HTTP requests targeting Casdoor endpoints
• Monitor application logs for attempts to inject HTML tags or JavaScript syntax into form configuration parameters
• Deploy Content Security Policy (CSP) headers to restrict inline script execution and report violations
• Conduct regular security audits of stored form customization content for malicious payloads

Monitoring Recommendations

• Enable verbose logging for all modifications to form customization settings in Casdoor
• Set up alerts for CSP violation reports indicating attempted inline script execution
• Monitor for unusual patterns in form configuration changes, particularly by low-privilege users
• Implement browser-based anomaly detection for JavaScript execution patterns on Casdoor pages

How to Mitigate CVE-2026-5468

Immediate Actions Required

• Audit all existing form customization fields (formCss, formCssMobile, formSideHtml) for malicious content and sanitize or remove any suspicious entries
• Restrict access to form customization features to trusted administrators only
• Implement strict Content Security Policy headers to prevent inline script execution
• Consider temporarily disabling form customization functionality until a patch is available

Patch Information

At the time of publication, the vendor (Casbin) has not released an official security patch for this vulnerability. The vendor was contacted early about this disclosure but did not respond. Users should monitor the official Casdoor repository and security advisories for updates. For additional context and updates, see VulDB Submission #781770.

Workarounds

• Implement server-side input validation to reject HTML tags and JavaScript content in form customization fields
• Deploy a Web Application Firewall with XSS protection rules in front of Casdoor instances
• Apply strict Content Security Policy headers with script-src 'self' to block inline JavaScript execution
• Limit form customization privileges to only highly trusted administrator accounts

# Example Content Security Policy header configuration for nginx
# Add to your Casdoor server configuration
add_header Content-Security-Policy "default-src 'self'; script-src 'self'; style-src 'self' 'unsafe-inline'; img-src 'self' data:; frame-ancestors 'none';" always;