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Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')

CVE-2026-9086

High
7.3/10

Summary

A flaw was found in Keycloak. A remote attacker with administrative privileges, specifically those with `manage-client` permission or access to client registration endpoints, could bypass client Uniform Resource Identifier (URI) validation. This is achieved by registering a malicious client with a specially crafted redirect URI using a case-insensitive `javascript:` or `data:` scheme. This Cross-Site Scripting (XSS) vulnerability allows for arbitrary code execution in the Keycloak origin when a victim clicks the crafted link, such as in the logout flow or the Admin Console.

  • LOW
  • NETWORK
  • HIGH
  • UNCHANGED
  • REQUIRED
  • LOW
  • HIGH
  • NONE

CWE-79 - Cross Site Scripting

Cross-Site Scripting, commonly referred to as XSS, is the most dominant class of vulnerabilities. It allows an attacker to inject malicious code into a pregnable web application and victimize its users. The exploitation of such a weakness can cause severe issues such as account takeover, and sensitive data exfiltration. Because of the prevalence of XSS vulnerabilities and their high rate of exploitation, it has remained in the OWASP top 10 vulnerabilities for years.

References

Advisory Timeline

  • Published