---
id: CVE-2025-2559
title: A flaw was found in Keycloak
summary: >-
  A flaw was found in Keycloak. When the configuration uses JWT tokens for
  authentication, the tokens are cached until expiration. If a client uses JWT
  tokens with an excessively long expiration time, for example, 24 or 48 hours,
  the cache…
severity: medium
cvss: 4.9
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H'
cwe:
  - CWE-770
vendor: Red Hat
product: keycloak
affected:
  - keycloak >= 23.0.0 < 26.0.11
  - keycloak >= 26.1.0 < 26.1.5
  - keycloak-services
  - rhbk/keycloak-operator-bundle (all versions)
  - rhbk/keycloak-rhel9 (all versions)
  - rhbk/keycloak-rhel9-operator (all versions)
  - keycloak-services (all versions)
published: '2025-03-25'
updated: '2026-09-21'
sourceUpdated: '2026-09-21T06:17:00.170'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2025-2559'
references:
  - url: 'https://access.redhat.com/errata/RHSA-2025:4335'
    label: secalert@redhat.com
  - url: 'https://access.redhat.com/errata/RHSA-2025:4336'
    label: secalert@redhat.com
  - url: 'https://access.redhat.com/security/cve/CVE-2025-2559'
    label: secalert@redhat.com
  - url: 'https://bugzilla.redhat.com/show_bug.cgi?id=2353868'
    label: secalert@redhat.com
  - url: >-
      https://github.com/keycloak/keycloak/commit/a10c8119d4452b866b90a9019b2cc159919276ca
    label: secalert@redhat.com
  - url: 'https://github.com/keycloak/keycloak/issues/38576'
    label: secalert@redhat.com
  - url: >-
      https://security.access.redhat.com/data/csaf/v2/vex/2025/cve-2025-2559.json
  - url: 'https://www.cve.org/CVERecord?id=CVE-2025-2559'
  - url: 'https://nvd.nist.gov/vuln/detail/CVE-2025-2559'
tags:
  - nvd
  - cve.org
  - csaf
  - vex
  - red-hat
ssvc:
  exploitation: none
  automatable: 'no'
  technicalImpact: partial
  timestamp: '2025-03-31T16:31:49.361189Z'
epss: 0.00683
epssPercentile: 0.50677
ingestedAt: '2026-09-21T06:32:37.142Z'
patched:
  - build_of_keycloak 26.0
  - build_of_keycloak
---

## Overview

A flaw was found in Keycloak. When the configuration uses JWT tokens for authentication, the tokens are cached until expiration. If a client uses JWT tokens with an excessively long expiration time, for example, 24 or 48 hours, the cache can grow indefinitely, leading to an OutOfMemoryError. This issue could result in a denial of service condition, preventing legitimate users from accessing the system.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.

## Vendor advisories

- **RHSA-2025:4335** · Red Hat · fixed in: Red Hat build of Keycloak 26.0 · released 2025-04-29 · [advisory](https://access.redhat.com/errata/RHSA-2025:4335)
- **RHSA-2025:4336** · Red Hat · fixed in: Red Hat Build of Keycloak · released 2025-04-29 · [advisory](https://access.redhat.com/errata/RHSA-2025:4336)
- **Red Hat VEX** · Moderate · affected: Red Hat Single Sign-On 7 · no fix planned: Red Hat Single Sign-On 7 · updated 2026-09-21 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2025/cve-2025-2559.json)