Keycloak 26.2 < 26.2.15 / 26.4 < 26.4.11 / 26.5 < 26.5.7 Multiple Vulnerabilities

high Nessus Plugin ID 330085

Synopsis

The remote host is affected by multiple vulnerabilities.

Description

Keycloak installed on the remote host is 26.2.x prior to 26.2.15, 26.4.x prior to 26.4.11, 26.5.x prior to 26.5.7 are affected by multiple vulnerabilities:

- A privilege escalation flaw exists due to improper isolation in the SingleUseObjectProvider. An unauthenticated, remote attacker can forge authorization codes and potentially obtain admin-capable access tokens. (CVE-2026-4282)

- A denial of service flaw exists in the OpenID Connect token endpoint. An unauthenticated, remote attacker can exhaust server CPU and memory by sending an excessively long scope parameter.
(CVE-2026-4634)

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

Solution

Upgrade Keycloak to version 26.2.15 / 26.4.11 / 26.5.7 or later.

Plugin Details

Severity: High

ID: 330085

File Name: keycloak_26_2_15.nasl

Version: 1.1

Type: Local

Agent: unix

Family: Misc.

Published: 7/27/2026

Updated: 7/27/2026

Configuration: Enable thorough checks (optional)

Supported Sensors: Nessus Agent, Nessus

Risk Information

VPR

Risk Factor: Medium

Score: 4.3

Percentile: 53.59

CVSS v2

Risk Factor: High

Base Score: 7.8

Vector: CVSS2#AV:N/AC:L/Au:N/C:N/I:N/A:C

CVSS Score Source: CVE-2026-4634

CVSS v3

Risk Factor: High

Base Score: 7.5

Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Vulnerability Information

CPE: cpe:/a:keycloak:keycloak

Required KB Items: Host/local_checks_enabled, Host/uname, installed_sw/Keycloak

Patch Publication Date: 4/2/2026

Vulnerability Publication Date: 4/2/2026

Reference Information

CVE: CVE-2026-4282, CVE-2026-4634

IAVB: 2026-B-0201

Detections

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