Dify — Xss (CVE-2026-21866)
Date: 2026-03
Affected: dify/dify
Attack vector: xss
Category: vulnerability-disclosure
Severity: Medium
CVE: CVE-2026-21866
CWE: CWE-79
CVSS: 5.4 (CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N)

Dify is an open-source LLM app development platform. Prior to 1.11.2, Dify is vulnerable to a stored XSS issue when rendering Mermaid diagrams within chats. This occurs because Dify’s default Mermaid configuration uses securityLevel: loose, which allows potentially unsafe content to execute. This vulnerability is fixed in 1.11.2.


Mitigations:

Architectural layers (MAESTRO):