---
id: "GHSA-37j9-56gh-j2r7"
kind: "vulnerability"
aliases: ["GHSA-37j9-56gh-j2r7"]
title: "Duplicate Advisory: Keycloak vulnerable to cross-site scripting (xss) via case-insensitive uri validation bypass"
severity: "high"
cvss: 7.3
epss: null
exploited: false
status: "withdrawn"
category: "package"
products: [{"name": "org.keycloak:keycloak-services", "fixed": [], "affected": "< 26.6.4", "ecosystem": "maven"}]
ecosystems: ["maven"]
tags: ["cwe-79", "java", "keycloak", "package", "self-hosted"]
not_affected_if: ["keycloak-26.6.4-or-later", "no-client-registration-access"]
published_at: "2026-06-25T18:30:41+00:00"
first_seen_at: "2026-10-29T16:39:02+00:00"
updated_at: "2026-10-29T16:39:55+00:00"
sources: [{"source": "ghsa", "url": "https://github.com/advisories/GHSA-37j9-56gh-j2r7", "first_seen_at": "2026-10-29T16:39:02+00:00"}]
---

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

Keycloak's client URI validation can be bypassed with a mixed-case javascript: or data: redirect URI, so a registered client can run script in the Keycloak origin. The sources say an attacker with manage-client rights or client registration access can plant the link, and a victim who clicks it (for example in the logout flow or the Admin Console) runs the attacker's code.

_Summary, check and fix written by a model from the sources; labelled as such._

## Affected

- maven:org.keycloak:keycloak-services affected < 26.6.4 fixed ?

## Fix

- `maven:org.keycloak:keycloak-services` affected below `26.6.4`; the sources do not name a separate fixed version for other branches
- Withdrawn duplicate; see GHSA-v3f7-2p4r-mwfw for the live advisory

## Timeline

- 2026-10-29T16:39:02+00:00 ghsa https://github.com/advisories/GHSA-37j9-56gh-j2r7

## From the sources

### Duplicate Advisory
This advisory has been withdrawn because it is a duplicate of GHSA-v3f7-2p4r-mwfw. This link is maintained to preserve external references.

### Original 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.

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_Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai_