CVE-2026-4634Network attack vector

Unauthenticated service interruption via oversized OIDC scope

Published Apr 2, 2026 · Updated Apr 2, 2026

Denial of service in Red Hat build of Keycloak allows remote attackers to interrupt the server via an oversized OIDC token scope. TokenManager parsed the entire scope parameter again for every scope name while resolving organization client scopes, and TokenEndpoint imposed no parameter-length limit. An unauthenticated POST to an enabled realm's token endpoint can consume enough CPU and processing time to deny authentication service.

CVSS severity7.5
High
EPSS probability0.52%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Denial of service in Red Hat build of Keycloak allows remote attackers to interrupt the server via an oversized OIDC token scope. TokenManager parsed the entire scope parameter again for every scope name while resolving organization client scopes, and TokenEndpoint imposed no parameter-length limit. An unauthenticated POST to an enabled realm's token endpoint can consume enough CPU and processing time to deny authentication service.

The record

CVE
CVE-2026-4634
Published
Apr 2, 2026
Updated
Apr 2, 2026
Vendor
389 Directory Server
Product
Red Hat build of Keycloak
Classifications
CWE-1050, T1499.003
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Apr 2, 2026CVE publishedPublication date reported by the CVE source.
  2. Apr 2, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Affected versions are unavailable in this record. Check the vendor advisory for version and patch details.

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

389 Directory Server · Red Hat build of KeycloakAffected versions are unavailable in this record.

Published CVSS scores

7.5Red Hat, Inc.CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
7.5redhat-SADPCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-1050Excessive Platform Resource Consumption within a Loop
T1499.003Application Exhaustion Flood

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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