CVE-2026-18571
Description
A flaw was found in the user creation component of Keycloak when Fine-Grained Admin Permissions V2 (FGAP V2) is enabled. This issue allows a sub-administrator with permission to create users to add those users to any group, even groups the sub-administrator is not authorized to manage. This could lead to unauthorized access to sensitive information or elevated privileges for the newly created users.
Statement
The Red Hat Product Security team has assessed the severity of this vulnerability as Moderate, given that it requires the non-default Fine-Grained Admin Permissions V2 to be enabled and the attacker must already possess high-level sub-administrator privileges. Successful exploitation allows an attacker to bypass group membership restrictions during user creation, potentially leading to unauthorized privilege escalation for new users. The vulnerability's root cause is a missing authorization check for group assignments within the user creation API payload.
Mitigation
Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability.
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
The following CVSS metrics and score provided are preliminary and subject to review.
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 6.6 | 7.2 | 6.6 |
| Attack Vector | Network | Network | Network |
| Attack Complexity | High | Low | High |
| Privileges Required | High | High | High |
| User Interaction | None | None | None |
| Scope | Unchanged | Unchanged | Unchanged |
| Confidentiality | High | High | High |
| Integrity Impact | High | High | High |
| Availability Impact | High | High | High |
Vector
Red Hat: CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:H
NVD: CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H
cve.org: CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:H
Understanding the Weakness (CWE)
Confidentiality
Technical Impact: Read Application Data; Read Files or Directories
An attacker could read sensitive data, either by reading the data directly from a data store that is not restricted, or by accessing insufficiently-protected, privileged functionality to read the data.
Integrity
Technical Impact: Modify Application Data; Modify Files or Directories
An attacker could modify sensitive data, either by writing the data directly to a data store that is not restricted, or by accessing insufficiently-protected, privileged functionality to write the data.
Access Control
Technical Impact: Gain Privileges or Assume Identity; Bypass Protection Mechanism
An attacker could gain privileges by modifying or reading critical data directly, or by accessing privileged functionality.
Availability
Technical Impact: DoS: Crash, Exit, or Restart; DoS: Resource Consumption (CPU); DoS: Resource Consumption (Memory); DoS: Resource Consumption (Other)
An attacker could gain unauthorized access to resources on the system and excessively consume those resources, leading to a denial of service.
Acknowledgements
Red Hat would like to thank robinho11842 for reporting this issue.
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