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)
Published · last modified .
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.
EPSS exploit prediction
EPSS: 0.002 (11.0th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 11th percentile — 11.0% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.002 · newest: 0.002 · change: 0.000
Affected products
- Dify
- Langgenius Dify — versions < 1.11.2
Weakness classification (CWE)
References
- github.com/langgenius/dify/security/advisories/GHSA-qpv6-75c2-75h4 (Exploit, Vendor Advisory)
- github.com/langgenius/dify/pull/29811 (Patch, Issue Tracking)
- github.com/langgenius/dify/commit/ae17537470bba417a8971fff705dd82ecb043564 (Patch)
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.