CVE-2026-18203
Full vulnerability record from the local CVENow database.
Description
A flaw was found in the group policy evaluation logic of Keycloak, an identity and access management solution. When a group policy is set to extend permissions to child groups, the system incorrectly uses a simple text-based prefix check to verify group membership. This allows a user who belongs to a different group with a similar starting name to bypass security checks and gain unauthorized access to administrative functions or protected resources.
Severity
MEDIUM
CVSS score
6.5
(v3.1)
Vulnerability status
Modified
Source identifier
Published
2026-07-31 08:16:27.010000
Last modified
2026-11-06 18:18:09.537000
View original CVE JSON
{
"id": "CVE-2026-18203",
"sourceIdentifier": "[email protected]",
"published": "2026-07-31T08:16:27.010",
"lastModified": "2026-11-06T18:18:09.537",
"vulnStatus": "Modified",
"cveTags": [],
"descriptions": [
{
"lang": "en",
"value": "A flaw was found in the group policy evaluation logic of Keycloak, an identity and access management solution. When a group policy is set to extend permissions to child groups, the system incorrectly uses a simple text-based prefix check to verify group membership. This allows a user who belongs to a different group with a similar starting name to bypass security checks and gain unauthorized access to administrative functions or protected resources."
}
],
"affected": [
{
"source": "[email protected]",
"affectedData": [
{
"vendor": "Red Hat",
"product": "Red Hat build of Keycloak 26.6",
"defaultStatus": "affected",
"collectionURL": "https://catalog.redhat.com/software/containers/",
"packageName": "rhbk/keycloak-operator-bundle",
"cpes": [
"cpe:/a:redhat:build_keycloak:26.6::el9"
],
"versions": [
{
"version": "26.6.8-2",
"lessThan": "*",
"versionType": "rpm",
"status": "unaffected"
}
]
},
{
"vendor": "Red Hat",
"product": "Red Hat build of Keycloak 26.6",
"defaultStatus": "affected",
"collectionURL": "https://catalog.redhat.com/software/containers/",
"packageName": "rhbk/keycloak-rhel9",
"cpes": [
"cpe:/a:redhat:build_keycloak:26.6::el9"
],
"versions": [
{
"version": "26.6-24",
"lessThan": "*",
"versionType": "rpm",
"status": "unaffected"
}
]
},
{
"vendor": "Red Hat",
"product": "Red Hat build of Keycloak 26.6",
"defaultStatus": "affected",
"collectionURL": "https://catalog.redhat.com/software/containers/",
"packageName": "rhbk/keycloak-rhel9-operator",
"cpes": [
"cpe:/a:redhat:build_keycloak:26.6::el9"
],
"versions": [
{
"version": "26.6-24",
"lessThan": "*",
"versionType": "rpm",
"status": "unaffected"
}
]
},
{
"vendor": "Red Hat",
"product": "Red Hat build of Keycloak 26.6.8",
"defaultStatus": "unaffected",
"collectionURL": "https://access.redhat.com/downloads/content/package-browser/",
"packageName": "keycloak-services",
"cpes": [
"cpe:/a:redhat:build_keycloak:26.6::el9"
]
},
{
"vendor": "Red Hat",
"product": "Red Hat build of Keycloak 26.6.8",
"defaultStatus": "unaffected",
"collectionURL": "https://access.redhat.com/downloads/content/package-browser/",
"packageName": "rhbk-keycloak-rhel9/rhbk-keycloak-rhel9",
"cpes": [
"cpe:/a:redhat:build_keycloak:26.6::el9"
]
},
{
"vendor": "Red Hat",
"product": "Red Hat build of Keycloak 26.6.8",
"defaultStatus": "unaffected",
"collectionURL": "https://access.redhat.com/downloads/content/package-browser/",
"packageName": "rhbk-openshift-rhel9/rhbk-openshift-rhel9",
"cpes": [
"cpe:/a:redhat:build_keycloak:26.6::el9"
]
},
{
"vendor": "Red Hat",
"product": "Red Hat Data Grid 8",
"defaultStatus": "unaffected",
"collectionURL": "https://access.redhat.com/downloads/content/package-browser/",
"packageName": "keycloak-services",
"cpes": [
"cpe:/a:redhat:jboss_data_grid:8"
]
},
{
"vendor": "Red Hat",
"product": "Red Hat JBoss Enterprise Application Platform Expansion Pack",
"defaultStatus": "unaffected",
"collectionURL": "https://access.redhat.com/jbossnetwork/restricted/listSoftware.html",
"packageName": "keycloak-services",
"cpes": [
"cpe:/a:redhat:jbosseapxp"
]
},
{
"vendor": "Red Hat",
"product": "Red Hat Single Sign-On 7",
"defaultStatus": "unaffected",
"collectionURL": "https://access.redhat.com/downloads/content/package-browser/",
"packageName": "keycloak-services",
"cpes": [
"cpe:/a:redhat:red_hat_single_sign_on:7"
]
}
]
}
],
"metrics": {
"cvssMetricV31": [
{
"source": "[email protected]",
"type": "Secondary",
"cvssData": {
"version": "3.1",
"vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N",
"baseScore": 6.5,
"baseSeverity": "MEDIUM",
"attackVector": "NETWORK",
"attackComplexity": "LOW",
"privilegesRequired": "LOW",
"userInteraction": "NONE",
"scope": "UNCHANGED",
"confidentialityImpact": "NONE",
"integrityImpact": "HIGH",
"availabilityImpact": "NONE"
},
"exploitabilityScore": 2.8,
"impactScore": 3.6
}
],
"ssvcV203": [
{
"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
"ssvcData": {
"timestamp": "2026-07-31T23:20:24.753622Z",
"id": "CVE-2026-18203",
"options": [
{
"exploitation": "none"
},
{
"automatable": "no"
},
{
"technicalImpact": "partial"
}
],
"role": "CISA Coordinator",
"version": "2.0.3"
}
}
]
},
"weaknesses": [
{
"source": "[email protected]",
"type": "Secondary",
"description": [
{
"lang": "en",
"value": "CWE-863"
}
]
}
],
"configurations": [
{
"nodes": [
{
"operator": "OR",
"negate": false,
"cpeMatch": [
{
"vulnerable": true,
"criteria": "cpe:2.3:a:redhat:build_of_keycloak:-:*:*:*:-:*:*:*",
"matchCriteriaId": "E5C930CB-4EAD-497B-A44B-D880F2A1F85B"
}
]
}
]
}
],
"references": [
{
"url": "https://access.redhat.com/errata/RHSA-2026:95761",
"source": "[email protected]"
},
{
"url": "https://access.redhat.com/errata/RHSA-2026:95762",
"source": "[email protected]"
},
{
"url": "https://access.redhat.com/security/cve/CVE-2026-18203",
"source": "[email protected]",
"tags": [
"Vendor Advisory"
]
},
{
"url": "https://bugzilla.redhat.com/show_bug.cgi?id=2508291",
"source": "[email protected]",
"tags": [
"Issue Tracking",
"Vendor Advisory"
]
}
]
}