CVE-2026-21866— Dify - Stored XSS in chat
Quick assessment
Affected
langgenius dify
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.
dify是LangGenius开源的一个开源的 LLM 应用程序开发平台。 dify 1.11.2之前版本存在跨站脚本漏洞，该漏洞源于渲染聊天中的Mermaid图表时默认配置安全级别宽松，可能导致存储型跨站脚本。
Possible ATT&CK Techniques 1 AI
T1059 · Command and Scripting Interpreter
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I. Basic Information for CVE-2026-21866
Vulnerability Information
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Vulnerability Title
Dify - Stored XSS in chat
Source: CVE Program / CVE List V5
Vulnerability Description
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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:P/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N
Source: CVE Program / CVE List V5
Vulnerability Type
在Web页面生成时对输入的转义处理不恰当(跨站脚本)
Source: CVE Program / CVE List V5
Vulnerability Title
dify 跨站脚本漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
dify是LangGenius开源的一个开源的 LLM 应用程序开发平台。 dify 1.11.2之前版本存在跨站脚本漏洞，该漏洞源于渲染聊天中的Mermaid图表时默认配置安全级别宽松，可能导致存储型跨站脚本。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)
Affected Products
| Vendor | Product | Affected Versions | CPE | Subscribe |
|---|---|---|---|---|
| langgenius | dify | < 1.11.2 | - |
|
II. Public POCs for CVE-2026-21866
| # | POC Description | Source Link | Shenlong Link |
|---|
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Patches & Fixes for CVE-2026-21866 (2)
-
fix: mermaid graph (#29811) · langgenius/dify@ae17537 · GitHub x_refsource_MISC
Vendor Advisories for CVE-2026-21866 (1)
-
Dify - Stored XSS in chat · Advisory · langgenius/dify · GitHub x_refsource_CONFIRM
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V. Comments for CVE-2026-21866
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