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Keycloak CVE-2026-18212

| EUVDEUVD-2026-80828 HIGH
Memory Leak (CWE-401)
2026-09-16 redhat GHSA-wgrv-cjmx-4vfw
7.5
CVSS 3.1 · Vendor: redhat
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Severity by source

Vendor (redhat) PRIMARY
7.5 HIGH
AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Primary rating from Vendor (redhat) · only source for this CVE.

CVSS VectorVendor: redhat

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

Lifecycle Timeline

2
Analysis Generated
Sep 16, 2026 - 16:43 vuln.today
CVE Published
Sep 16, 2026 - 14:54 cve.org
HIGH 7.5

DescriptionCVE.org

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.

AnalysisAI

Native memory exhaustion in Keycloak's SAML Redirect Binding allows an unauthenticated remote attacker to degrade or halt the service by repeatedly sending malformed SAML requests that leak zlib-allocated native memory. Red Hat Build of Keycloak, Red Hat Single Sign-On 7, Red Hat Data Grid 8, and the Red Hat JBoss EAP Expansion Pack are all affected because they embed the same SAML handling code. …

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Vulnerability AssessmentAI

Risk Assessment All available signals point to a genuine but bounded (availability-only) network DoS. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in.
Remediation Patch availability is confirmed per vendor advisory: Red Hat has published errata RHSA-2026:68276, RHSA-2026:68277, RHSA-2026:68278, and RHSA-2026:68280 (https://access.redhat.com/errata/RHSA-2026:68276, https://access.redhat.com/errata/RHSA-2026:68277, https://access.redhat.com/errata/RHSA-2026:68278, https://access.redhat.com/errata/RHSA-2026:68280), so administrators should identify the erratum matching their product stream (Red Hat Build of Keycloak, RH-SSO 7, Data Grid 8, or JBoss EAP Expansion Pack) and apply the updated build; the advisory at https://access.redhat.com/security/cve/CVE-2026-18212 should be consulted for the exact fixed versions. … Detailed patch versions, workarounds, and compensating controls in full report.

Recommended ActionAI

Within 24 hours, inventory every deployment of Keycloak, Red Hat Build of Keycloak, Red Hat Single Sign-On 7, Red Hat Data Grid 8, and the JBoss EAP Expansion Pack, and determine which of them expose SAML handling (specifically the SAML Redirect Binding) to untrusted or internet-facing networks; for any instance where that binding is not operationally required, disable or firewall it, and in all other cases place the SAML endpoints behind a reverse proxy or WAF with request-size caps, per-source rate limiting, and connection limits, while enabling native-memory and garbage-collection alerting so that exhaustion is detected before a full outage. …

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CVE-2026-18212 vulnerability details – vuln.today

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