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Vulnerability · Published Sep 16, 2026 · Assigned by redhat

CVE-2026-18212Keycloak-services: keycloak-services: saml redirect deflate helpers leak native zlib state

High 7.5

In plain English

A high-severity memory leak in Red Hat build of Keycloak 26.4 from Red Hat. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.7% (higher than 53% of all known vulnerabilities).

Severity (CVSS 3.1)7.5High
Exploit odds (30 days)0.7%top 46.5% of all CVEs
Exploited in the wildNo reportsCISA SSVC: none
Attack toolingNoneno public tooling known

Official 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.

Affected products (as reported)

VendorProductVersions
Red Hat Red Hat build of Keycloak 26.4 see references
Red Hat Red Hat build of Keycloak 26.4 see references
Red Hat Red Hat build of Keycloak 26.4 see references
Red Hat Red Hat build of Keycloak 26.4.16 see references
Red Hat Red Hat build of Keycloak 26.4.16 see references
Red Hat Red Hat build of Keycloak 26.6 see references
Red Hat Red Hat build of Keycloak 26.6 see references
Red Hat Red Hat build of Keycloak 26.6 see references
Red Hat Red Hat build of Keycloak 26.6.7 see references
Red Hat Red Hat build of Keycloak 26.6.7 see references
Red Hat Red Hat build of Keycloak 26.6.7 see references
Red Hat Red Hat Data Grid 8 see references
Red Hat Red Hat JBoss Enterprise Application Platform Expansion Pack see references
Red Hat Red Hat Single Sign-On 7 see references

Weakness: CWE-401 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

References