CVE-2026-9803: Keycloak services Keycloak Has An Out-of-bounds Read Vulnerability
MODERATECVE-2026-9803 is a MODERATE (CVSS 5.3) keycloak has an out-of-bounds read vulnerability (CWE-125: Out-of-bounds Read) affecting Keycloak services libraries in the Maven ecosystem. The issue involves keycloak has an out-of-bounds read. Remediation is available by upgrading affected packages to version 26.6.3.
CVE-2026-9803 at a Glance
Security Impact
CVSS: 5.3
The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L).
How to Fix CVE-2026-9803
To remediate this vulnerability, upgrade all affected Keycloak services dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.
<dependency>
<groupId>org.keycloak</groupId>
<artifactId>keycloak-services</artifactId>
<version>Latest secure release</version>
</dependency><dependency>
<groupId>org.keycloak</groupId>
<artifactId>keycloak-services</artifactId>
<version>26.6.3</version>
</dependency>Run the following command in your project directory to verify that all resolved dependencies use the patched release:
mvn dependency:tree -Dincludes=org.keycloakHow to Check if You Are Affected
To determine whether your Java application is affected by CVE-2026-9803, inspect your build dependencies using the Maven Dependency Plugin:
mvn dependency:tree -Dincludes=org.keycloakAnalyze the terminal output to locate any version of Keycloak services in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 26.6.3), your application is affected.
Note: The mvn dependency:tree -Dincludes=org.keycloak command inspects the resolved dependency graph declared in your project's POM files; it does not perform automated security scanning or inspect runtime dynamic classpaths. Always verify runtime container classpaths and shaded JARs.
Technical Details
Vulnerability Mechanism & Technical Analysis
This vulnerability is classified under CWE-125: Out-of-bounds Read, where the product reads data past the end, or before the beginning, of the intended buffer. In Keycloak services, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.
Source Advisory Statement
CVE-2026-9803 Affected Keycloak services Versions
2 component(s)| Product / Package | Ecosystem | Affected Versions | Fixed Version |
|---|---|---|---|
|
org.keycloak:keycloak-services
|
Maven |
≤ 26.4.7
|
|
|
org.keycloak:keycloak-services
|
Maven |
≥ 26.5.0
< 26.6.3
|
26.6.3
|
References
Frequently Asked Questions
What is CVE-2026-9803?
Which Keycloak services versions are affected?
What version fixes CVE-2026-9803?
Is keycloak-services affected?
What is the CVSS score of CVE-2026-9803?
What CWE is associated with CVE-2026-9803?
How can I check Maven dependencies for CVE-2026-9803?
Machine-readable OSV JSON
OSV v1.5 Schema
{
"schema_version" : "1.4.0",
"id" : "GHSA-cpf7-j4cf-vqx4",
"modified" : "2026-07-01T21:27:37Z",
"published" : "2026-05-28T06:31:10Z",
"aliases" : [ "CVE-2026-9803" ],
"summary" : "Keycloak has an Out-of-bounds Read",
"details" : "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.",
"severity" : [ {
"type" : "CVSS_V3",
"score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L"
} ],
"affected" : [ {
"package" : {
"ecosystem" : "Maven",
"name" : "org.keycloak:keycloak-services"
},
"ranges" : [ {
"type" : "ECOSYSTEM",
"events" : [ {
"introduced" : "0"
}, {
"last_affected" : "26.4.7"
} ]
} ]
}, {
"package" : {
"ecosystem" : "Maven",
"name" : "org.keycloak:keycloak-services"
},
"ranges" : [ {
"type" : "ECOSYSTEM",
"events" : [ {
"introduced" : "26.5.0"
}, {
"fixed" : "26.6.3"
} ]
} ]
} ],
"references" : [ {
"type" : "ADVISORY",
"url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-9803"
}, {
"type" : "WEB",
"url" : "https://github.com/keycloak/keycloak/issues/49433"
}, {
"type" : "WEB",
"url" : "https://github.com/keycloak/keycloak/pull/49500"
}, {
"type" : "WEB",
"url" : "https://github.com/keycloak/keycloak/pull/49617"
}, {
"type" : "WEB",
"url" : "https://github.com/keycloak/keycloak/pull/49618"
}, {
"type" : "WEB",
"url" : "https://github.com/keycloak/keycloak/commit/2b8692499e907e6205be0bd9c8a4da5d46f6ca30"
}, {
"type" : "WEB",
"url" : "https://github.com/keycloak/keycloak/commit/3fc06909cc93eb5c4739a712fa350de625812e04"
}, {
"type" : "WEB",
"url" : "https://github.com/keycloak/keycloak/commit/ef06df91d344c7e99fcb82987ef6adb854f30789"
}, {
"type" : "WEB",
"url" : "https://access.redhat.com/errata/RHSA-2026:25097"
}, {
"type" : "WEB",
"url" : "https://access.redhat.com/errata/RHSA-2026:25098"
}, {
"type" : "WEB",
"url" : "https://access.redhat.com/errata/RHSA-2026:30049"
}, {
"type" : "WEB",
"url" : "https://access.redhat.com/errata/RHSA-2026:30050"
}, {
"type" : "WEB",
"url" : "https://access.redhat.com/security/cve/CVE-2026-9803"
}, {
"type" : "WEB",
"url" : "https://bugzilla.redhat.com/show_bug.cgi?id=2482465"
}, {
"type" : "PACKAGE",
"url" : "https://github.com/keycloak/keycloak"
} ],
"database_specific" : {
"cwe_ids" : [ "CWE-125" ],
"severity" : "MODERATE",
"github_reviewed" : true,
"github_reviewed_at" : "2026-07-01T21:27:37Z",
"nvd_published_at" : "2026-05-28T06:16:29Z"
}
}