high · 7.3 Patched

Keycloak vulnerable to cross-site scripting (xss) via case-insensitive uri validation bypass

CVE-2026-9086 · GHSA-v3f7-2p4r-mwfw · published 29 Oct 2026

How serious is it

  • Severity: high, CVSS score 7.3 out of 10.
  • No exploit prediction (EPSS) score yet.
  • Not on the CISA list of exploited vulnerabilities.
  • No public exploit in Exploit-DB.

Is your app affected by CVE-2026-9086?

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Who is affected

  • org.keycloak:keycloak-services (Maven) < 26.6.4

How to check

  1. Look for org.keycloak:keycloak-services in your lockfile and compare its version with the range above.
  2. Or paste your lockfile into the checker: it lists every package with a known vulnerability, this one included.

How to fix

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  1. Upgrade org.keycloak:keycloak-services to 26.6.4 or later, commit the lockfile and redeploy.
  2. If a vulnerable version was live, check your logs and rotate the secrets that server could read.

The advisory

### Description 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.

Check your whole app

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References

Merged from GitHub Advisory Database. Last updated 30 Oct 2026. All vulnerabilities · RSS · JSON

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