CVE-2026-9689

[CVE catalog]

Severity

Medium · CVSS 4.2CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:L/I:L/A:N

Published

May 27, 2026, 10:18:25 AM UTC

Source

[NVD] · [CVE record]

EPSS

0.32% · Oct 25, 2026

A flaw was found in Keycloak, an open-source identity and access management solution. When a client application is configured to accept broad redirect Uniform Resource Identifiers (URIs), a remote attacker can manipulate the authentication process by crafting a special web address. If a user clicks this link, the client application might incorrectly prioritize attacker-controlled information over legitimate data. This vulnerability, known as HTTP parameter pollution, could allow an attacker to bypass security measures or gain unauthorized access to resources. keycloak: org.keycloak.protocol.oidc: HTTP Parameter Pollution in OIDC redirect URI allows response parameter duplication - #GHI-604 This Moderate severity flaw in Keycloak arises from HTTP parameter pollution when a client is configured with a wildcard redirect URI. An attacker could craft a malicious authorization URL that, if clicked by a user, may lead to the client application incorrectly processing attacker-controlled OIDC response parameters. Exploitation is contingent on the client application employing a 'first-wins' strategy for duplicate query parameters, which is not a universal behavior. The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.