Medium severity · published Jul 17, 2026
CVE-2026-16103
Keycloak-services: keycloak-services: incomplete fix for ciba brute-force lockout bypass at token redemption
4.3
CVSS
0.3%
EPSS
No
On KEV
Description
A flaw was found in the keycloak-services component of Keycloak. This issue is an incomplete fix for CVE-2026-9798, where brute-force protection checks were added to the Client-Initiated Backchannel Authentication (CIBA) initiation handler but were omitted from the token redemption handler. This allows an attacker with valid client credentials to obtain access and refresh tokens for a user account that has been locked due to brute-force protection, provided the authentication request was started before the lockout occurred and was approved by the user.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:N
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
Required
Confidentiality
Low
Integrity
None
Availability
None
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.3% · higher than 28% 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 · Red Hat
All versions, or not specified · source: vendor
BO
Build OF Keycloak · Redhat
All versions, or not specified · source: NVD
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-16103
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-16103
Vendor Advisory
https://access.redhat.com/security/cve/CVE-2026-16103
Issue Tracking
https://bugzilla.redhat.com/show_bug.cgi?id=2501736
More from Red Hat Build of Keycloak
9.8
CVE-2026-42581
Netty: HTTP/1.0 TE+CL Coexistence Bypasses Smuggling Sanitization
9.8
CVE-2026-33228
flatted: Prototype Pollution via parse()
9.1
CVE-2026-42584
Netty: HttpClientCodec response desynchronization
9.1
CVE-2026-42579
Netty: DNS Codec Input Validation Bypass in Netty (Encoder + Decoder)
8.2
CVE-2026-93569
Io.netty/netty-codec-http2: http/1 absolute-form host mismatch is translated to http/2 :authority, overriding the request-target authority
