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Fencer Vulns
high 7.5

CVE-2026-18212 json

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

published 2026-09-16 54 d ago modified 2026-09-16 53 d ago also EUVD-2026-80828

cvss
7.5
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.7%
EPSS 0.7% chance of exploitation in 30 days, percentile 53%
public exploits
0
none known

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 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.

Patch / fix

  • Red Hat Red Hat build of Keycloak 26.4 26.4-26, 26.4.16-2
  • Red Hat Red Hat build of Keycloak 26.6 26.6-20, 26.6.7-3

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-18212 updated cvss 7.5

keycloak-services: keycloak-services: SAML Redirect DEFLATE helpers leak native zlib state

  • Red Hat Data Grid 8 keycloak-services 23.0.7 Red Hat Single Sign-On 7 keycloak-services 23.0.7
    affected: workaround, no fix planned “Will not fix”
  • Red Hat build of Keycloak 26.4 rhbk/keycloak-rhel9 26.4-26, rhbk/keycloak-rhel9-operator 26.4-26, rhbk/keycloak-operator-bundle 26.4.16-2
    fixed: vendor fix RHSA-2026:68276
  • Red Hat build of Keycloak 26.4.16
    fixed: vendor fix RHSA-2026:68280
  • Red Hat build of Keycloak 26.6 rhbk/keycloak-rhel9 26.6-20, rhbk/keycloak-rhel9-operator 26.6-20, rhbk/keycloak-operator-bundle 26.6.7-3
    fixed: vendor fix RHSA-2026:68277
  • Red Hat build of Keycloak 26.6.7
    fixed: vendor fix RHSA-2026:68278
  • Red Hat JBoss Enterprise Application Platform Expansion Pack keycloak-services 23.0.7
    not affected: component not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
none
Automatable
yes
Technical impact
partial
Assessed
53 d ago

Exploit prediction

0.70% chance of exploitation in the next 30 days, higher than 53% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Affected products

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

Classification

Weakness
  • CWE-401 Missing Release of Memory after Effective Lifetime

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.