CVE-2026-2575: Keycloak Denial of Service Vulnerability

MODERATE
Advisory Identifier: GHSA-xv6h-r36f-3gp5
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CVSS 5.3
CWE-409
Published
Advisory Summary

CVE-2026-2575 is a MODERATE (CVSS 5.3) denial of service vulnerability (CWE-409: Improper Handling of Highly Compressed Data (Data Amplification)) affecting Keycloak libraries in the Maven ecosystem. The issue involves denial of service due to excessive samlrequest decompression. Remediation is available by upgrading affected packages to version 26.5.4.

CVE-2026-2575 at a Glance

CVE Identifier CVE-2026-2575
GHSA Identifier GHSA-xv6h-r36f-3gp5
Severity MODERATE
CVSS v3.1 Base Score 5.3
CWE Classification CWE-409: Improper Handling of Highly Compressed Data (Data Amplification)
Affected Product Keycloak
Package Ecosystem Maven
Published Date
Last Updated

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).

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

How to Fix CVE-2026-2575

To remediate this vulnerability, upgrade all affected Keycloak 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-saml-adapter-core fixed: 26.5.4 
<dependency>
    <groupId>org.keycloak</groupId>
    <artifactId>keycloak-saml-adapter-core</artifactId>
    <version>26.5.4</version>
</dependency>
org.keycloak:keycloak-saml-core fixed: 26.5.4 
<dependency>
    <groupId>org.keycloak</groupId>
    <artifactId>keycloak-saml-core</artifactId>
    <version>26.5.4</version>
</dependency>
org.keycloak:keycloak-services fixed: 26.5.4 
<dependency>
    <groupId>org.keycloak</groupId>
    <artifactId>keycloak-services</artifactId>
    <version>26.5.4</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-2026-2575, 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 in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 26.5.4), 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-409: Improper Handling of Highly Compressed Data (Data Amplification), where the product does not handle or incorrectly handles a compressed input with a very high compression ratio that produces a large output. In Keycloak, 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 unauthenticated remote attacker can trigger an application level Denial of Service (DoS) by sending a highly compressed SAMLRequest through the SAML Redirect Binding. The server fails to enforce size limits during DEFLATE decompression, leading to an OutOfMemoryError (OOM) and subsequent process termination. This vulnerability allows an attacker to disrupt the availability of the service.

CVE-2026-2575 Affected Keycloak Versions

3 component(s)
Fixed Versions:
26.5.4
Product / Package Ecosystem Affected Versions Fixed Version
org.keycloak:keycloak-saml-adapter-core
maven/org.keycloak/keycloak-saml-adapter-core
Maven
< 26.5.4
26.5.4
org.keycloak:keycloak-saml-core
maven/org.keycloak/keycloak-saml-core
Maven
< 26.5.4
26.5.4
org.keycloak:keycloak-services
maven/org.keycloak/keycloak-services
Maven
< 26.5.4
26.5.4

References

NVD — CVE-2026-2575 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-2575
Keycloak Source Repository REPOSITORY
https://github.com/keycloak/keycloak/issues/46372
Security Fix Commit FIX COMMIT
https://github.com/keycloak/keycloak/commit/4f90ef67f698dfb45df0d2f4981271a7c8b47f04
access.redhat.com/errata/rhsa-2026:39... WEB
https://access.redhat.com/errata/RHSA-2026:3947
access.redhat.com/errata/rhsa-2026:39... WEB
https://access.redhat.com/errata/RHSA-2026:3948
access.redhat.com/errata/rhsa-2026:76... WEB
https://access.redhat.com/errata/RHSA-2026:76128
access.redhat.com/errata/rhsa-2026:76... WEB
https://access.redhat.com/errata/RHSA-2026:76129
access.redhat.com/errata/rhsa-2026:76... WEB
https://access.redhat.com/errata/RHSA-2026:76130
access.redhat.com/errata/rhsa-2026:76... WEB
https://access.redhat.com/errata/RHSA-2026:76132
access.redhat.com/errata/rhsa-2026:76... WEB
https://access.redhat.com/errata/RHSA-2026:76134
Keycloak Security Information SECURITY
https://access.redhat.com/security/cve/CVE-2026-2575
bugzilla.redhat.com/show_bug.cgi WEB
https://bugzilla.redhat.com/show_bug.cgi?id=2440149
Keycloak Source Repository REPOSITORY
https://github.com/keycloak/keycloak

Frequently Asked Questions

What is CVE-2026-2575?
CVE-2026-2575 is a security vulnerability in Keycloak involving Denial of Service due to excessive SAMLRequest decompression under CWE-409: Improper Handling of Highly Compressed Data (Data Amplification).
Which Keycloak versions are affected?
Affected versions include releases prior to 26.5.4 across affected packages: org.keycloak:keycloak-saml-adapter-core, org.keycloak:keycloak-saml-core, org.keycloak:keycloak-services.
What version fixes CVE-2026-2575?
Upgrading to 26.5.4 (or the latest patched release for your respective branch) resolves the vulnerability.
Is keycloak-saml-adapter-core affected?
Yes, org.keycloak:keycloak-saml-adapter-core is affected in releases prior to 26.5.4. Upgrade your dependency to 26.5.4 or later.
Is keycloak-saml-core affected?
Yes, org.keycloak:keycloak-saml-core is affected in releases prior to 26.5.4. Upgrade your dependency to 26.5.4 or later.
What is the CVSS score of CVE-2026-2575?
CVE-2026-2575 has a CVSS v3.1 base score of 5.3 (MODERATE) with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L.
What CWE is associated with CVE-2026-2575?
CVE-2026-2575 is classified under CWE-409: Improper Handling of Highly Compressed Data (Data Amplification) (The product does not handle or incorrectly handles a compressed input with a very high compression ratio that produces a large output.).
How can I check Maven dependencies for CVE-2026-2575?
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-xv6h-r36f-3gp5",
  "modified" : "2026-10-06T18:31:15Z",
  "published" : "2026-03-18T06:31:20Z",
  "aliases" : [ "CVE-2026-2575" ],
  "summary" : "Keycloak: Denial of Service due to excessive SAMLRequest decompression",
  "details" : "A flaw was found in Keycloak. An unauthenticated remote attacker can trigger an application level Denial of Service (DoS) by sending a highly compressed SAMLRequest through the SAML Redirect Binding. The server fails to enforce size limits during DEFLATE decompression, leading to an OutOfMemoryError (OOM) and subsequent process termination. This vulnerability allows an attacker to disrupt the availability of the 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-saml-adapter-core"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "26.5.4"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "Maven",
      "name" : "org.keycloak:keycloak-saml-core"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "26.5.4"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "Maven",
      "name" : "org.keycloak:keycloak-services"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "26.5.4"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-2575"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/keycloak/keycloak/issues/46372"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/keycloak/keycloak/commit/4f90ef67f698dfb45df0d2f4981271a7c8b47f04"
  }, {
    "type" : "WEB",
    "url" : "https://access.redhat.com/errata/RHSA-2026:3947"
  }, {
    "type" : "WEB",
    "url" : "https://access.redhat.com/errata/RHSA-2026:3948"
  }, {
    "type" : "WEB",
    "url" : "https://access.redhat.com/errata/RHSA-2026:76128"
  }, {
    "type" : "WEB",
    "url" : "https://access.redhat.com/errata/RHSA-2026:76129"
  }, {
    "type" : "WEB",
    "url" : "https://access.redhat.com/errata/RHSA-2026:76130"
  }, {
    "type" : "WEB",
    "url" : "https://access.redhat.com/errata/RHSA-2026:76132"
  }, {
    "type" : "WEB",
    "url" : "https://access.redhat.com/errata/RHSA-2026:76134"
  }, {
    "type" : "WEB",
    "url" : "https://access.redhat.com/security/cve/CVE-2026-2575"
  }, {
    "type" : "WEB",
    "url" : "https://bugzilla.redhat.com/show_bug.cgi?id=2440149"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/keycloak/keycloak"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-409" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-03-18T20:19:33Z",
    "nvd_published_at" : "2026-03-18T04:17:16Z"
  }
}