Keycloak: Denial of Service due to excessive SAMLRequest decompression

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

5.3 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

EPSS

• CVE-2026-2575: 0.65% estimated exploitation activity in the next 30 days; percentile 51.12 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

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.

Published by the source

18 Mar 2026, 06:31 UTC

Last modified by the source

6 Oct 2026, 18:31 UTC

Source last checked

26 Oct 2026, 16:58 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-xv6h-r36f-3gp5

Preview the exact text before you copy it. Commands are read-only suggestions; review them before running anything.

# Patch Next advisory brief: CVE-2026-2575

Advisory: Keycloak: Denial of Service due to excessive SAMLRequest decompression
IDs: CVE-2026-2575, GHSA-xv6h-r36f-3gp5
Record: https://patchnext.com/advisories/cve-2026-2575 (revision 1, source checked 26 Oct 2026, 16:58 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 5.3)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: org.keycloak:keycloak-services 26.5.4; org.keycloak:keycloak-saml-core 26.5.4; org.keycloak:keycloak-saml-adapter-core 26.5.4. A vendor fix does not mean a deployment is fixed.

## Affected components
- Maven org.keycloak:keycloak-services: affected < 26.5.4; fixed in 26.5.4
- Maven org.keycloak:keycloak-saml-core: affected < 26.5.4; fixed in 26.5.4
- Maven org.keycloak:keycloak-saml-adapter-core: affected < 26.5.4; fixed in 26.5.4

## Suggested inspection (read-only)
- Maven org.keycloak:keycloak-services: check the installed version with your package manager.
- Maven org.keycloak:keycloak-saml-core: check the installed version with your package manager.
- Maven org.keycloak:keycloak-saml-adapter-core: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on org.keycloak:keycloak-services, org.keycloak:keycloak-saml-core, org.keycloak:keycloak-saml-adapter-core.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-xv6h-r36f-3gp5 (GitHub-reviewed advisory GHSA-xv6h-r36f-3gp5 lists affected ranges: Maven org.keycloak:keycloak-saml-adapter-core >=0 =0 =0 <26.5.4)

Commands are suggestions: review each one before running it.