CVE-2026-9803

mediumpriority · track · 0EPSS 0.004 · 36 %ileDEEUUS

grimoire priorityP3 · Track

Exploitable?

—

no known exploitation

Likely / severe?

0.42% (36th) EPSS

CVSS 5.3 · medium

Is it mine?

13 products

Check your exposure

Who says so?

5 sources

cnnvd · enisa_euvd · cert_bund · nvd

EPSS · scored 2026-10-27

A flaw was found in Keycloak's ClientRegistrationAuth component. A remote unauthenticated attacker can exploit this vulnerability by sending a specially crafted POST request with a malformed 'Authorization: Bearer' header to any client registration endpoint. This can lead to an ArrayIndexOutOfBoundsException, causing the server to return an HTTP 500 error and resulting in a Denial of Service (DoS) for the affected service.

cvss

Technical severity, 0–10. One row per scoring source.

5.3

010

base score 0–10 · higher = more severe · hover a vector to decode

v3.15.3mediumCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:Lsecondary · ENISA EU

v3.15.3mediumCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:Lsecondary · secalert@redhat.com USexploitability 3.9 · impact 1.4

v3.15.3mediumCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:Lsecondary · OSV

v3.14.9mediumCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L/E:Usecondary · CVSS-BT (t0sche)

ssvc

A stakeholder decision — act, attend, or track — from exploitation and impact.

Exploitation: none · Automatable: yes · Technical Impact: partialcoordinatorcisa_ssvcUS

weaknesses

The CWE weakness classes this flaw belongs to.

CWE-125USCWE-125US

affected products (13)

Products and version ranges known to be affected.

Open Source Keycloakall versionscert_bundDEcpe:/a:keycloak:keycloak:-
Open Source Keycloak <26.6.3all versionscert_bundDE
Open Source Keycloak <26.7.0all versionscert_bundDE
Red Hat Enterprise Linuxall versionscert_bundDEcpe:/o:redhat:enterprise_linux:-
Open Source Keycloak< 26.6.3cert_bundDE
Open Source Keycloak< 26.7.0cert_bundDE
Red Hat Red Hat build of Keycloak 26.4< 26.4-19enisa_euvdEU
Red Hat Red Hat build of Keycloak 26.4< 26.4.13-1enisa_euvdEU
Red Hat Red Hat build of Keycloak 26.6< 26.6-6enisa_euvdEU
Red Hat Red Hat build of Keycloak 26.6< 26.6.3-3enisa_euvdEU
redhat build of keycloakall versionsnvdUScpe:2.3:a:redhat:build_of_keycloak:*:*:*:*:*:*:*:*
Maven org.keycloak:keycloak-services≤ 26.4.7osvUSpkg:maven/org.keycloak/keycloak-services
Maven org.keycloak:keycloak-services26.5.0 → 26.6.3osvUSpkg:maven/org.keycloak/keycloak-services

advisories (2)

Vendor and ecosystem advisories describing this.

WID-SEC-W-2026-1708Keycloak: Mehrere SchwachstellenDeutsch2026-05-27csaf · cert_bundDE
Ein Angreifer kann mehrere Schwachstellen in Keycloak ausnutzen, um seine Privilegien zu erhöhen, um Informationen offenzulegen, um Sicherheitsvorkehrungen zu umgehen und um einen Denial of Service Angriff durchzuführen.
GHSA-cpf7-j4cf-vqx4Keycloak has an Out-of-bounds Read2026-05-28ghsa · osvUS
A flaw was found in Keycloak's ClientRegistrationAuth component. A remote unauthenticated attacker can exploit this vulnerability by sending a specially crafted POST request with a malformed 'Authorization: Bearer' header to any client registration endpoint. This can lead to an ArrayIndexOutOfBoundsException, causing the server to return an HTTP 500 error and resulting in a Denial of Service (DoS) for the affected service.

also known as (3)

Other names and identifiers for this entity.

sources

Which sources assert this record, and when.

cnnvd enisa_euvd cert_bund nvd osv NVD CVE.org MITRE

published 2026-05-28modified 2026-10-26

references (14)

External citations — patches, advisories, analysis.

scry

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