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Vulnerabilities

Vulnerability · CVE-2026-21866

Dify is an open-source LLM app development platform.

Published Mar 3, 2026 · catalog updated Jun 17, 2026 · Dify is an open-source

Check if you run it

No confirmed exploitation is on record for CVE-2026-21866. EPSS is 0.23%. Act only if a listed version of Dify is an open-source is installed.

Gaps on this record

  • The stored product name is a package slug. The name on this page is taken from the title (Dify is an open-source).
  • No version range is stored. A customer cannot check an installed version against this record.
  • No vendor fix or required action is stored. Compare the linked advisory before you change production.
Severity
Medium5.1
Known exploitation
Not in CISA/VulnCheck KEV
EPSS
0.23%
Remediation
Advisory link
Affected products
cpe dify/dify

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.

Are you affected?

Enter the version you run. The result uses only the ranges stored on this record.

The check returns affected, not affected, or incomplete. It does not guess a version that is missing from the record.

  • cpe dify/difyversion unspecified

How to fix CVE-2026-21866

What to do

Three questions, each answered from this record only. Confirm the vendor advisory before you patch.

Should you patch?

No confirmed exploitation is on record for CVE-2026-21866. EPSS is 0.23%. Act only if a listed version of Dify is an open-source is installed.

Which versions are affected?

Affected version ranges are not on this record. Compare the installed version with the linked vendor advisory before you change production.

What should an analyst verify?

CWE-79: Cross-site Scripting (XSS). EPSS 0.23%. There is no CISA KEV listing. No Exploit-DB or Metasploit reference is linked. Use the source links for the original advisory.

Code

The project this record applies to. Exploit listings stay in References.

Timeline

Detection, updates, and resolution for this record.

  1. Mar 3, 2026 · NIST NVD

    Detected

    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.

  2. Jun 17, 2026 · NIST NVD

    Updated

    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.

Sources

  • CVE.orgVulnerability recordCVE-2026-21866

    Official CVE identifier

    cve.org
  • FIRST EPSSExploitation probabilityCVE-2026-21866

    30-day exploitation probability 0.2%

    first.org
  • NIST NVDVulnerability recordCVE-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

    nvd.nist.gov

References

Freshness

Last verified in this catalog Oct 18, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.