CVE-2026-6619: Langgenius Dify XSS Vulnerability

CVE-2026-6619 Overview

A Cross-Site Scripting (XSS) vulnerability has been discovered in Langgenius Dify, an open-source LLM application development platform. The vulnerability exists in the openInNewTab function within the ImagePreview component located at web/app/components/base/image-uploader/image-preview.tsx. Improper sanitization of the filename argument allows remote attackers to inject malicious scripts, potentially compromising user sessions and application integrity.

Critical Impact

Remote attackers can inject arbitrary JavaScript code through manipulated filename parameters, enabling session hijacking, credential theft, and unauthorized actions on behalf of authenticated users.

Affected Products

• Langgenius Dify versions up to and including 1.13.3
• Dify ImagePreview component (web/app/components/base/image-uploader/image-preview.tsx)

Discovery Timeline

• 2026-04-20 - CVE-2026-6619 published to NVD
• 2026-04-22 - Last updated in NVD database

Technical Details for CVE-2026-6619

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 resides in the ImagePreview component's handling of user-supplied filename data when opening images in a new browser tab.

The openInNewTab function fails to properly sanitize or encode the filename parameter before incorporating it into the rendered output. This allows an attacker to craft a malicious filename containing JavaScript code that executes in the context of a victim's browser session when they interact with the affected component.

The attack requires user interaction (clicking to preview an image) and authenticated access to the Dify platform. However, the network-accessible nature of the vulnerability means it can be exploited remotely against any user with access to the affected component.

Root Cause

The root cause is insufficient input validation and output encoding in the openInNewTab function within the ImagePreview component. When processing the filename argument, the application fails to sanitize special characters and HTML/JavaScript content before rendering, allowing script injection through carefully crafted filenames.

Attack Vector

The vulnerability is exploitable via network access. An attacker can upload or reference an image with a maliciously crafted filename containing embedded JavaScript. When a victim user interacts with the ImagePreview component to open the image in a new tab, the unsanitized filename is processed, causing the injected script to execute in the victim's browser context.

The exploitation mechanism involves crafting a filename that breaks out of the expected rendering context and injects executable JavaScript. Technical details and proof-of-concept code are available through the GitHub Gist PoC and VulDB submission #792242.

Detection Methods for CVE-2026-6619

Indicators of Compromise

• Unusual JavaScript execution patterns originating from image preview interactions
• Filenames containing encoded script tags, event handlers (e.g., onerror, onload), or javascript: URIs
• Unexpected network requests to external domains following image preview actions
• Session tokens or authentication data being transmitted to unauthorized endpoints

Detection Strategies

• Implement Content Security Policy (CSP) headers to detect and block inline script execution attempts
• Monitor application logs for suspicious filename patterns containing HTML entities, script tags, or JavaScript event handlers
• Deploy Web Application Firewall (WAF) rules to detect XSS payloads in filename parameters
• Use browser-based XSS auditing and sanitization libraries to flag malicious content

Monitoring Recommendations

• Enable detailed logging for the ImagePreview component and related file upload functionality
• Monitor for anomalous user session behavior following image preview interactions
• Implement real-time alerting for CSP violation reports indicating blocked script execution attempts

How to Mitigate CVE-2026-6619

Immediate Actions Required

• Upgrade Langgenius Dify to a version newer than 1.13.3 when a patch becomes available
• Implement server-side filename sanitization to strip or encode potentially dangerous characters
• Apply Content Security Policy headers to prevent inline script execution
• Review and audit any user-uploaded filenames currently stored in the system

Patch Information

At the time of disclosure, the vendor (Langgenius) was contacted but did not respond. Users should monitor the official Dify GitHub repository for security updates. Additional vulnerability tracking information is available via VulDB #358254.

Workarounds

• Implement input sanitization middleware to encode or reject filenames containing special characters (<, >, ", ', &, script tags)
• Deploy a reverse proxy or WAF with XSS filtering capabilities to inspect and sanitize request/response content
• Restrict access to the ImagePreview component to trusted users until a patch is available
• Apply CSP headers with script-src 'self' to prevent execution of injected inline scripts

# Example Content Security Policy header configuration for Nginx
add_header Content-Security-Policy "default-src 'self'; script-src 'self'; object-src 'none'; base-uri 'self';" always;