---
id: CVE-2026-107889
title: A flaw was found in the login theme rendering component of Keycloak
summary: >-
  A flaw was found in the login theme rendering component of Keycloak. The issue
  occurs because the security filter responsible for cleaning user input can be
  bypassed, allowing a realm administrator to store malicious scripts in display
  f…
severity: medium
cvss: 5.5
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:L/I:L/A:N'
cwe:
  - CWE-79
published: '2026-10-09'
updated: '2026-10-09'
sourceUpdated: '2026-10-09T05:16:44.583'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-107889'
references:
  - url: 'https://access.redhat.com/security/cve/CVE-2026-107889'
    label: secalert@redhat.com
  - url: 'https://bugzilla.redhat.com/show_bug.cgi?id=2548355'
    label: secalert@redhat.com
  - url: >-
      https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-107889.json
  - url: 'https://www.cve.org/CVERecord?id=CVE-2026-107889'
  - url: 'https://nvd.nist.gov/vuln/detail/CVE-2026-107889'
tags:
  - nvd
  - csaf
  - vex
  - red-hat
ingestedAt: '2026-10-09T05:26:07.005Z'
vendor: Red Hat
product: Red Hat Build of Keycloak
affected:
  - build_of_keycloak
---

## Overview

A flaw was found in the login theme rendering component of Keycloak. The issue occurs because the security filter responsible for cleaning user input can be bypassed, allowing a realm administrator to store malicious scripts in display fields. This could result in unauthorized JavaScript execution in the browsers of users visiting the login page, potentially leading to data exposure or session interference.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.

## Vendor advisories

- **Red Hat VEX** · Moderate · affected: Red Hat Build of Keycloak · no fix planned: Red Hat Build of Keycloak · updated 2026-10-09 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-107889.json)