XSS in Dify
CVE-2026-21866
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.
Vulnerability class: XSS (Cross-Site Scripting)
EPSS: 0.002 (12.4th percentile) — read the EPSS interpretation.
CVSS v3 metric
CVSS v3 base score 5.4 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N.
Affected products
- Dify
- Langgenius Dify — versions < 1.11.2
Weakness classification (CWE)
References
- security-advisories@github.com (x_refsource_CONFIRM, Exploit, Vendor Advisory)
- security-advisories@github.com (Patch, x_refsource_MISC, Issue Tracking)
- security-advisories@github.com (Patch, x_refsource_MISC)
Frequently asked questions
- What is CVE-2026-21866?
- CVE-2026-21866 is a medium-severity vulnerability in Dify, classified under Cross-site Scripting. CVSS score: 5.4/10. Published 2026-03-03.
- How severe is CVE-2026-21866?
- Medium severity. CVSS v3 base score is 5.4 out of 10.