Medium severity · published May 27, 2026
CVE-2026-9689
Keycloak: org.keycloak.protocol.oidc: http parameter pollution in oidc redirect uri allows response parameter duplication - #ghi-604
4.2
CVSS
0.3%
EPSS
No
On KEV
Description
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.
CVSS vector
CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:L/I:L/A:N
Attack vector
Network
Complexity
High
Privileges
None
User interaction
Required
Confidentiality
Low
Integrity
Low
Availability
None
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.3% · higher than 25% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
RH
Red Hat build of Keycloak 26.4 · Red Hat
All versions, or not specified · source: vendor
RH
Red Hat build of Keycloak 26.6 · Red Hat
All versions, or not specified · source: vendor
BO
Build OF Keycloak · Redhat
All versions, or not specified · source: NVD
Affected product
RH
Red Hat build of Keycloak 26.4
Red Hat
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