A session fixation vulnerability was found in Keycloak's login-actions endpoints. An unauthenticated attacker could exploit this flaw by pre-creating an authentication session and tricking a victim into visiting a maliciously crafted link. By leveraging the /login-actions/restart endpoint—which processes session handles without adequate CSRF protection or cookie ownership validation—an attacker can reset the authentication flow state. This causes Single Sign-On (SSO) to authenticate the victim transparently upon clicking the link, allowing the attacker to hijack the required-action form without needing the victim's credentials. A successful exploit could lead to complete account takeover, including highly privileged administrative accounts.
{
"cwe_ids": [
"CWE-290"
],
"github_reviewed": true,
"github_reviewed_at": "2026-06-04T15:37:17Z",
"nvd_published_at": "2026-05-19T12:16:19Z",
"severity": "HIGH"
}