Description
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.
Published: 2026-09-16
Score: 7.5 High
EPSS: < 1% Very Low
KEV: No
Impact: Denial of Service
Action: Assess Impact
AI Analysis

Impact

Keycloak’s SAML Redirect Binding uses custom DEFLATE helpers that do not release native zlib state after use, creating a memory leak. An unauthenticated attacker can send a large number of malformed SAML requests, exhausting the application’s native memory and causing a denial of service. The weakness is a classic memory‑leak flaw (CWE‑401).

Affected Systems

The vulnerability affects Red Hat builds of Keycloak versions 26.4 (including 26.4.16), 26.6 and 26.6.7, as well as Red Hat Data Grid 8, the JBoss Enterprise Application Platform Expansion Pack, and Red Hat Single Sign‑On 7. These products are identified through the associated CPE strings. Administrators should verify whether their installations include any of these affected releases.

Risk and Exploitability

The CVSS score of 7.5 classifies the issue as high severity. The EPSS score indicates a very low current exploitation probability, and the vulnerability is not listed in the CISA KEV catalog. Based on the description, the attack vector involves sending repeated malformed SAML redirect requests to an unauthenticated Keycloak service, which could lead to memory exhaustion and service disruption if the leak is not mitigated.

Generated by OpenCVE AI on September 18, 2026 at 00:16 UTC.

Remediation

Vendor Workaround

Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability.

OpenCVE Recommended Actions

  • Check for and apply any available Red Hat errata updates that target Keycloak versions 26.4, 26.6, or 26.6.7, such as those referenced in RHSA-2026:68276, RHSA-2026:68277, and RHSA-2026:68278.
  • If an official patch is not yet released, enforce strict rate limiting or blocking of SAML redirect requests from untrusted sources at the network perimeter to reduce repeated memory‑exhaustion attempts.
  • Monitor application memory usage and warning logs for abnormal growth patterns and respond promptly if memory consumption rises unexpectedly.

Generated by OpenCVE AI on September 18, 2026 at 00:16 UTC.

Tracking

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Advisories

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History

Thu, 17 Sep 2026 12:15:00 +0000

Type Values Removed Values Added
References
Metrics threat_severity

None

 threat_severity

Important

Wed, 16 Sep 2026 19:30:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'yes', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Wed, 16 Sep 2026 16:00:00 +0000

Type Values Removed Values Added
CPEs cpe:/a:redhat:build_keycloak: cpe:/a:redhat:build_keycloak:26.4::el9
cpe:/a:redhat:build_keycloak:26.6::el9
References

Wed, 16 Sep 2026 15:00:00 +0000

Type Values Removed Values Added
Description 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.
Title Keycloak-services: keycloak-services: saml redirect deflate helpers leak native zlib state
First Time appeared Redhat
Redhat build Keycloak
Redhat jboss Data Grid
Redhat jbosseapxp
Redhat red Hat Single Sign On
Weaknesses CWE-401
CPEs cpe:/a:redhat:build_keycloak:
cpe:/a:redhat:jboss_data_grid:8
cpe:/a:redhat:jbosseapxp
cpe:/a:redhat:red_hat_single_sign_on:7
Vendors & Products Redhat
Redhat build Keycloak
Redhat jboss Data Grid
Redhat jbosseapxp
Redhat red Hat Single Sign On
References
Metrics cvssV3_1

{'score': 7.5, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H'}

Subscriptions

Redhat Build Keycloak Jboss Data Grid Jbosseapxp Red Hat Single Sign On
cve-icon MITRE

Status: PUBLISHED

Assigner: redhat

Published:

Updated: 2026-09-16T18:35:27.170Z

Reserved: 2026-07-29T08:31:24.186Z

Link: CVE-2026-18212

cve-icon Vulnrichment

Updated: 2026-09-16T18:25:12.993Z

cve-icon NVD

Status : Awaiting Analysis

Published: 2026-09-16T15:17:33.257

Modified: 2026-09-16T19:42:43.623

Link: CVE-2026-18212

cve-icon Redhat

Severity : Important

Publid Date: 2026-09-16T12:57:23Z

Links: CVE-2026-18212 - Bugzilla

cve-icon OpenCVE Enrichment

Updated: 2026-09-18T00:30:16Z

Weaknesses
  • CWE-401

    Missing Release of Memory after Effective Lifetime