CVE-2026-9704: Keycloak server spi private Keycloak Vulnerable To Improper Validation Vulnerability

MODERATE
Advisory Identifier: GHSA-rr5q-3xwr-f323
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CVSS 6.8
CWE-1284
Published
Advisory Summary

CVE-2026-9704 is a MODERATE (CVSS 6.8) keycloak vulnerable to improper validation vulnerability (CWE-1284: Improper Validation of Specified Quantity in Input) affecting Keycloak server spi private libraries in the Maven ecosystem. The issue involves keycloak vulnerable to improper validation of specified quantity in input. Remediation is available by upgrading affected packages to version 26.6.3.

CVE-2026-9704 at a Glance

CVE Identifier CVE-2026-9704
GHSA Identifier GHSA-rr5q-3xwr-f323
Severity MODERATE
CVSS v3.1 Base Score 6.8
CWE Classification CWE-1284: Improper Validation of Specified Quantity in Input
Affected Product Keycloak server spi private
Package Ecosystem Maven
Published Date
Last Updated

Security Impact

CVSS: 6.8

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:N).

Attack Vector Network (AV:N)
Attack Complexity High (AC:H)
Privileges Required Low (PR:L)
User Interaction None (UI:N)
Scope Unchanged (S:U)
Confidentiality High (C:H)
Integrity High (I:H)
Availability None (A:N)

How to Fix CVE-2026-9704

To remediate this vulnerability, upgrade all affected Keycloak server spi private dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

org.keycloak:keycloak-server-spi-private fixed: 26.6.3 
<dependency>
    <groupId>org.keycloak</groupId>
    <artifactId>keycloak-server-spi-private</artifactId>
    <version>26.6.3</version>
</dependency>
org.keycloak:keycloak-services fixed: 26.6.3 
<dependency>
    <groupId>org.keycloak</groupId>
    <artifactId>keycloak-services</artifactId>
    <version>26.6.3</version>
</dependency>
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

mvn dependency:tree -Dincludes=org.keycloak

How to Check if You Are Affected

To determine whether your Java application is affected by CVE-2026-9704, inspect your build dependencies using the Maven Dependency Plugin:

mvn dependency:tree -Dincludes=org.keycloak

Analyze the terminal output to locate any version of Keycloak server spi private 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-1284: Improper Validation of Specified Quantity in Input, where the product receives input that is expected to specify a quantity (such as size or length), but it does not validate or incorrectly validates that the quantity has the required properties. In Keycloak server spi private, 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

A flaw was found in Keycloak. An authenticated user with low privileges can exploit this vulnerability by sending an oversized subject_token JSON Web Token (JWT) to the TokenEndpoint. When the token exceeds a 4000-character limit, it is silently dropped, causing the system to fall back to client credentials. This allows the user to gain the permissions of the client's service account, leading to privilege escalation.

CVE-2026-9704 Affected Keycloak server spi private Versions

2 component(s)
Fixed Versions:
26.6.3
Product / Package Ecosystem Affected Versions Fixed Version
org.keycloak:keycloak-server-spi-private
maven/org.keycloak/keycloak-server-spi-private
Maven
< 26.6.3
26.6.3
org.keycloak:keycloak-services
maven/org.keycloak/keycloak-services
Maven
< 26.6.3
26.6.3

References

NVD — CVE-2026-9704 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-9704
Keycloak server spi private Source Repository REPOSITORY
https://github.com/keycloak/keycloak/issues/49435
Keycloak server spi private Source Repository REPOSITORY
https://github.com/keycloak/keycloak/pull/49472
Security Fix Commit FIX COMMIT
https://github.com/keycloak/keycloak/commit/f1e5b7776c42938d0782fd5846346b8f75c815e6
access.redhat.com/errata/rhsa-2026:25... WEB
https://access.redhat.com/errata/RHSA-2026:25097
access.redhat.com/errata/rhsa-2026:25... WEB
https://access.redhat.com/errata/RHSA-2026:25098
access.redhat.com/errata/rhsa-2026:30... WEB
https://access.redhat.com/errata/RHSA-2026:30049
access.redhat.com/errata/rhsa-2026:30... WEB
https://access.redhat.com/errata/RHSA-2026:30050
Keycloak server spi private Security Information SECURITY
https://access.redhat.com/security/cve/CVE-2026-9704
bugzilla.redhat.com/show_bug.cgi WEB
https://bugzilla.redhat.com/show_bug.cgi?id=2481877
Keycloak server spi private Source Repository REPOSITORY
https://github.com/keycloak/keycloak

Frequently Asked Questions

What is CVE-2026-9704?
CVE-2026-9704 is a security vulnerability in Keycloak server spi private involving Keycloak Vulnerable to Improper Validation of Specified Quantity in Input under CWE-1284: Improper Validation of Specified Quantity in Input.
Which Keycloak server spi private versions are affected?
Affected versions include releases prior to 26.6.3 across affected packages: org.keycloak:keycloak-server-spi-private, org.keycloak:keycloak-services.
What version fixes CVE-2026-9704?
Upgrading to 26.6.3 (or the latest patched release for your respective branch) resolves the vulnerability.
Is keycloak-server-spi-private affected?
Yes, org.keycloak:keycloak-server-spi-private is affected in releases prior to 26.6.3. Upgrade your dependency to 26.6.3 or later.
Is keycloak-services affected?
Yes, org.keycloak:keycloak-services is affected in releases prior to 26.6.3. Upgrade your dependency to 26.6.3 or later.
What is the CVSS score of CVE-2026-9704?
CVE-2026-9704 has a CVSS v3.1 base score of 6.8 (MODERATE) with vector string CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:N.
What CWE is associated with CVE-2026-9704?
CVE-2026-9704 is classified under CWE-1284: Improper Validation of Specified Quantity in Input (The product receives input that is expected to specify a quantity (such as size or length), but it does not validate or incorrectly validates that the quantity has the required properties.).
How can I check Maven dependencies for CVE-2026-9704?
Run the dependency tree command: 'mvn dependency:tree -Dincludes=org.keycloak'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-rr5q-3xwr-f323",
  "modified" : "2026-07-01T19:09:45Z",
  "published" : "2026-05-27T15:33:25Z",
  "aliases" : [ "CVE-2026-9704" ],
  "summary" : "Keycloak Vulnerable to Improper Validation of Specified Quantity in Input",
  "details" : "A flaw was found in Keycloak. An authenticated user with low privileges can exploit this vulnerability by sending an oversized subject_token JSON Web Token (JWT) to the TokenEndpoint. When the token exceeds a 4000-character limit, it is silently dropped, causing the system to fall back to client credentials. This allows the user to gain the permissions of the client's service account, leading to privilege escalation.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Maven",
      "name" : "org.keycloak:keycloak-server-spi-private"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "26.6.3"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "Maven",
      "name" : "org.keycloak:keycloak-services"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "26.6.3"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-9704"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/keycloak/keycloak/issues/49435"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/keycloak/keycloak/pull/49472"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/keycloak/keycloak/commit/f1e5b7776c42938d0782fd5846346b8f75c815e6"
  }, {
    "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-2026-9704"
  }, {
    "type" : "WEB",
    "url" : "https://bugzilla.redhat.com/show_bug.cgi?id=2481877"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/keycloak/keycloak"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-1284" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-07-01T19:09:45Z",
    "nvd_published_at" : "2026-05-27T14:17:40Z"
  }
}