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

Quick assessment

Affected
Red Hat Red Hat build of Keycloak 26.4
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Keycloak（一个开源的身份与访问管理解决方案）的 SAML 重定向绑定（SAML Redirect Binding）实现中存在一个缺陷。该问题源于自定义的 DEFLATE 压缩与解压缩辅助函数在使用后未能释放原生 zlib 内存。未经身份验证的攻击者可以通过发送反复畸形的 SAML 请求来利用此缺陷，从而导致原生内存耗尽，进而引发服务中断（拒绝服务，DoS）。

CVSS 7.5 · High
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I. Basic Information for CVE-2026-18212

Vulnerability Information
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Vulnerability Title
Keycloak-services: keycloak-services: saml redirect deflate helpers leak native zlib state
Source: CVE Program / CVE List V5
Vulnerability 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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
在移除最后引用时对内存的释放不恰当(内存泄露)
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
Red Hat Red Hat build of Keycloak 26.4 26.4-26 ~ * cpe:/a:redhat:build_keycloak:26.4::el9
Red Hat Red Hat build of Keycloak 26.4 26.4-26 ~ * cpe:/a:redhat:build_keycloak:26.4::el9
Red Hat Red Hat build of Keycloak 26.4 26.4.16-2 ~ * cpe:/a:redhat:build_keycloak:26.4::el9
Red Hat Red Hat build of Keycloak 26.4.16 - cpe:/a:redhat:build_keycloak:26.4::el9
Red Hat Red Hat build of Keycloak 26.4.16 - cpe:/a:redhat:build_keycloak:26.4::el9
Red Hat Red Hat build of Keycloak 26.6 26.6-20 ~ * cpe:/a:redhat:build_keycloak:26.6::el9
Red Hat Red Hat build of Keycloak 26.6 26.6.7-3 ~ * cpe:/a:redhat:build_keycloak:26.6::el9
Red Hat Red Hat build of Keycloak 26.6 26.6-20 ~ * cpe:/a:redhat:build_keycloak:26.6::el9
Red Hat Red Hat build of Keycloak 26.6.7 - cpe:/a:redhat:build_keycloak:26.6::el9
Red Hat Red Hat build of Keycloak 26.6.7 - cpe:/a:redhat:build_keycloak:26.6::el9
Red Hat Red Hat build of Keycloak 26.6.7 - cpe:/a:redhat:build_keycloak:26.6::el9
Red Hat Red Hat Data Grid 8 - cpe:/a:redhat:jboss_data_grid:8
Red Hat Red Hat JBoss Enterprise Application Platform Expansion Pack - cpe:/a:redhat:jbosseapxp
Red Hat Red Hat Single Sign-On 7 - cpe:/a:redhat:red_hat_single_sign_on:7

II. Public POCs for CVE-2026-18212

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III. Intelligence Information for CVE-2026-18212

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Vendor Advisories for CVE-2026-18212 (2)

Other References for CVE-2026-18212 (4)

Same Patch Batch · Red Hat · 2026-09-16 · 9 CVEs total

CVE-2026-74909 8.1 HIGH Keycloak-services: keycloak-services: incomplete fix for cve-2026-15573 allows policy enfo
CVE-2026-79651 7.5 HIGH Keycloak-services: keycloak-services: unauthenticated dos via unbounded locale caching
CVE-2026-42784 7.4 HIGH Sequoia-openpgp: sequoia-openpgp: cryptographic integrity compromise via key flag confusio
CVE-2026-17526 7.2 HIGH Keycloak-services: keycloak-services: privilege escalation via impersonation role allows t
CVE-2026-92615 6.6 MEDIUM Flightctl: flightctl: package-global go-git https transport mutated per-repo -- cross-tena
CVE-2026-92358 6.4 MEDIUM Keycloak-services: keycloak-services: residual cross-browser account-link proof allows sil
CVE-2026-92091 5.9 MEDIUM Jwcrypto: jwcrypto: denial of service via o(n^2) duplicate check on unbounded jwk key_ops
CVE-2026-19607 5.3 MEDIUM Keycloak-services: keycloak-services: broker-originated username collision causes account

IV. Related Vulnerabilities

Same product: Red Hat build of Keycloak 26.4
Same vendor: Red Hat
Same weakness: CWE-401

V. Comments for CVE-2026-18212

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