CVE-2026-107889 Keycloak-services: keycloak-services: stored xss on login page via kcsanitize bypass
A stored XSS vulnerability in Keycloak's login page allows realm administrators to inject malicious scripts, potentially compromising user sessions and data.
- Exploited in the wild
- Not known
- Login needed
- An administrator
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-107889?
CVE-2026-107889 is a medium-severity cross-site scripting vulnerability in Red Hat Build of Keycloak, published on 9 Oct 2026. An attacker needs administrator access to exploit it, with no action from the victim.
Official description
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.
Weakness: CWE-79
Which versions are affected by CVE-2026-107889?
How do I fix CVE-2026-107889?
No fix has been published for CVE-2026-107889 yet. Limit exposure of the affected software until one is available.
Escape output for the context it lands in and set a strict Content Security Policy. Upgrading the affected component is the real fix. More about Cross-site scripting.
Is CVE-2026-107889 being exploited?
There is no known exploitation of CVE-2026-107889 in the wild and no public exploit code.
Sources
Also known as GHSA-gv8g-wx99-6r59.