Description
A flaw was found in Keycloak. An unauthenticated remote attacker can trigger an application level Denial of Service (DoS) by sending a highly compressed SAMLRequest through the SAML Redirect Binding. The server fails to enforce size limits during DEFLATE decompression, leading to an OutOfMemoryError (OOM) and subsequent process termination. This vulnerability allows an attacker to disrupt the availability of the service.
Affected products
| Vendor | Product | Affected | Fixed |
|---|---|---|---|
| Red Hat | Red Hat build of Keycloak 26.4 | — | — |
| Red Hat | Red Hat build of Keycloak 26.4.10 | — | — |
| Red Hat | Red Hat Single Sign-On 7.6.13 | — | — |
| Red Hat | Red Hat Single Sign-On 7.6 for RHEL 7 | — | — |
| Red Hat | Red Hat Single Sign-On 7.6 for RHEL 8 | — | — |
| Red Hat | Red Hat Single Sign-On 7.6 for RHEL 9 | — | — |
| Red Hat | RHEL-8 based Middleware Containers | — | — |
Fixed in Linux distributions
Distributions backport fixes, so the version that fixes this vulnerability differs per release — upgrade to at least the version shown. From the distributions' security trackers and advisories.
Red Hat
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Red Hat Single Sign On 7 | rh-sso7-keycloak +1 | 18.0.20-1.redhat_00001.1.el7sso | RHSA-2026:76130, RHSA-2026:76129, RHSA-2026:76128 |
Wolfi
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Wolfi rolling | keycloak-26.4-iamguarded-compat | No fix yet | — |
Affected packages
| Ecosystem | Package | Affected | Fixed | Record |
|---|---|---|---|---|
| Maven | org.keycloak:keycloak-saml-adapter-core | < 26.5.4 | 26.5.4 | GHSA-xv6h-r36f-3gp5 |
| Maven | org.keycloak:keycloak-saml-core | < 26.5.4 | 26.5.4 | GHSA-xv6h-r36f-3gp5 |
| Maven | org.keycloak:keycloak-services | < 26.5.4 | 26.5.4 | GHSA-xv6h-r36f-3gp5 |
Advisories 4
- RHSA-2026:76130 Red Hat Security Advisory: Red Hat Single Sign-On 7.6.13 security update on RHEL 9 Red Hat Security Advisories (RHSA) · Oct 20, 2026
- RHSA-2026:76129 Red Hat Security Advisory: Red Hat Single Sign-On 7.6.13 security update on RHEL 8 Red Hat Security Advisories (RHSA) · Oct 20, 2026
- RHSA-2026:76128 Red Hat Security Advisory: Red Hat Single Sign-On 7.6.13 security update on RHEL 7 Red Hat Security Advisories (RHSA) · Oct 20, 2026
- WID-SEC-2026-0416 Keycloak: Schwachstelle ermöglicht Denial of Service BSI CERT-Bund (WID) · Mar 17, 2026
References
- RHSA-2026:3947 vendor-advisory
- RHSA-2026:3948 vendor-advisory
- RHSA-2026:76128 vendor-advisory
- RHSA-2026:76129 vendor-advisory
- RHSA-2026:76130 vendor-advisory
- RHSA-2026:76132 vendor-advisory
- RHSA-2026:76134 vendor-advisory
- https://access.redhat.com/security/cve/CVE-2026-2575 vdb-entry
- RHBZ#2440149 issue-tracking