---
id: CVE-2026-18212
title: >-
  A flaw was found in the SAML Redirect Binding implementation of Keycloak, an
  open-source identity and access management solution
summary: >-
  A flaw was found in the SAML Redirect Binding implementation of Keycloak, an
  open-source identity and access management solution. The issue occurs because
  the custom DEFLATE compression and decompression helpers fail to release
  native zl…
severity: high
cvss: 7.5
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H'
cwe:
  - CWE-401
vendor: Red Hat
product: keycloak-rhel9-container
affected:
  - keycloak-rhel9-container (all versions)
  - keycloak-rhel9-operator-container (all versions)
  - rhbk/keycloak-operator-bundle (all versions)
  - keycloak-services
  - rhbk-openshift-rhel9/rhbk-openshift-rhel9
  - keycloak-rhel9-container (all versions)
  - keycloak-rhel9-operator-bundle-container (all versions)
  - keycloak-rhel9-operator-container (all versions)
  - keycloak-services
  - rhbk-keycloak-rhel9/rhbk-keycloak-rhel9
  - rhbk-openshift-rhel9/rhbk-openshift-rhel9
  - keycloak-services (all versions)
  - keycloak-services
  - keycloak-services (all versions)
patched:
  - build_of_keycloak 26.4
  - build_of_keycloak 26.4.16
  - build_of_keycloak 26.6.7
published: '2026-09-16'
updated: '2026-09-16'
sourceUpdated: '2026-09-16T19:42:43.623'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-18212'
references:
  - url: 'https://access.redhat.com/errata/RHSA-2026:68276'
    label: secalert@redhat.com
  - url: 'https://access.redhat.com/errata/RHSA-2026:68277'
    label: secalert@redhat.com
  - url: 'https://access.redhat.com/errata/RHSA-2026:68278'
    label: secalert@redhat.com
  - url: 'https://access.redhat.com/errata/RHSA-2026:68280'
    label: secalert@redhat.com
  - url: 'https://access.redhat.com/security/cve/CVE-2026-18212'
    label: secalert@redhat.com
  - url: 'https://bugzilla.redhat.com/show_bug.cgi?id=2508307'
    label: secalert@redhat.com
  - url: >-
      https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-18212.json
  - url: 'https://www.cve.org/CVERecord?id=CVE-2026-18212'
  - url: 'https://nvd.nist.gov/vuln/detail/CVE-2026-18212'
tags:
  - nvd
  - cve.org
  - csaf
  - vex
  - red-hat
ssvc:
  exploitation: none
  automatable: 'yes'
  technicalImpact: partial
  timestamp: '2026-09-16T18:25:11.882582Z'
ingestedAt: '2026-09-16T14:57:28.029Z'
epss: 0.00523
epssPercentile: 0.41919
---

## Overview

A flaw was found in the SAML Redirect Binding implementation of Keycloak, an open-source identity and access management solution. The issue occurs because the custom DEFLATE compression and decompression helpers fail to release native zlib memory after use. An unauthenticated attacker can exploit this by sending repeated malformed SAML requests, leading to native memory exhaustion and a denial of service.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.

## Vendor advisories

- **RHSA-2026:68276** · Red Hat · fixed in: Red Hat build of Keycloak 26.4 · released 2026-09-16 · [advisory](https://access.redhat.com/errata/RHSA-2026:68276)
- **RHSA-2026:68280** · Red Hat · fixed in: Red Hat build of Keycloak 26.4.16 · released 2026-09-16 · [advisory](https://access.redhat.com/errata/RHSA-2026:68280)
- **RHSA-2026:68278** · Red Hat · fixed in: Red Hat build of Keycloak 26.6.7 · released 2026-09-16 · [advisory](https://access.redhat.com/errata/RHSA-2026:68278)
- **Red Hat VEX** · Important · affected: Red Hat Data Grid 8, Red Hat Single Sign-On 7 · no fix planned: Red Hat Data Grid 8, Red Hat Single Sign-On 7 · updated 2026-09-16 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-18212.json)
- **RHSA-2026:68277** · Red Hat · fixed in: Red Hat build of Keycloak 26.6 · released 2026-09-16 · [advisory](https://access.redhat.com/errata/RHSA-2026:68277)