CVE-2026-92857
Description
Keycloak provides a Dynamic Client Registration feature that allows users with specific tokens to register their own applications. A flaw in how Keycloak validates these registration requests allows an attacker to create a malicious application that forges identity information. By mapping their own user profile details to protected fields like the user ID (sub) or intended audience (aud), an attacker can generate signed security tokens that make them appear to be a different user. This could allow an attacker to impersonate other users or gain unauthorized access to services that rely on these tokens for identity verification.
Statement
The Red Hat Product Security team has assessed the severity of this vulnerability as Important, given that exploitation requires the attacker to possess a valid Initial Access Token and a realm account. Successful exploitation allows an attacker to forge identity claims in signed tokens, leading to user impersonation across access tokens, ID tokens, and UserInfo responses. The vulnerability's root cause is a lack of validation for the claim.name field in protocol mapper configurations during Dynamic Client Registration.
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.
--- CME Mitigation Guidance (2026-11-06) ---
Disclaimer: The following mitigation solutions are provided as a courtesy, pending the application of an official patch. This content was generated utilizing AI tools in conjunction with data from https://cmetaxonomy.org. Customers are advised to independently evaluate and test these temporary mitigations within their own infrastructure.
The highest-value action is to validate protocol mapper claim.name configurations during Dynamic Client Registration to deny mapping to reserved identity claims: upgrade to Red Hat build of Keycloak 26.4.17, 26.6.8 (or the corresponding fixed Red Hat builds), which validate and reject protocol mapper configurations in Dynamic Client Registration that assign reserved claims to claim.name, closing all 2 injection vectors (Dynamic Client Registration protocol mapper configuration mapping user profile attributes to the sub claim, Dynamic Client Registration protocol mapper configuration mapping user profile attributes to the aud claim). Until patched, this is a concern on Keycloak deployments enabling Dynamic Client Registration where users possess an Initial Access Token and editable realm profile attributes, so restrict issuance of Initial Access Tokens, monitor new client registrations, and restrict user capabilities to edit profile attributes. As a compensating measure, detect unauthorized Dynamic Client Registration creations and protocol mapper changes by alerting on configuration drift against declared realm baselines and log Dynamic Client Registration events and mapper configurations to a SIEM to identify unauthorized clients mapping reserved token claims. These controls limit blast radius and contain exploitation, but they do not fix the underlying unvalidated protocol mapper claim.name defect — apply the upstream patch to fully remediate.
Highest-impact CME: CME-1315 Allowlist-Preferred Input Validation (Deny-by-Default Filtering) (high)
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).
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 8.1 | N/A | 8.1 |
| Attack Vector | Network | N/A | Network |
| Attack Complexity | Low | N/A | Low |
| Privileges Required | Low | N/A | Low |
| User Interaction | None | N/A | None |
| Scope | Unchanged | N/A | Unchanged |
| Confidentiality | High | N/A | High |
| Integrity Impact | High | N/A | High |
| Availability Impact | None | N/A | None |
Vector
Red Hat: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N
cve.org: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N
Understanding the Weakness (CWE)
Availability
Technical Impact: DoS: Crash, Exit, or Restart; DoS: Resource Consumption (CPU); DoS: Resource Consumption (Memory)
An attacker could provide unexpected values and cause a program crash or arbitrary control of resource allocation, leading to excessive consumption of resources such as memory and CPU.
Confidentiality
Technical Impact: Read Memory; Read Files or Directories
An attacker could read confidential data if they are able to control resource references.
Integrity,Confidentiality,Availability
Technical Impact: Modify Memory; Execute Unauthorized Code or Commands
An attacker could use malicious input to modify data or possibly alter control flow in unexpected ways, including arbitrary command execution.
Acknowledgements
Red Hat would like to thank Eurico Nicacio (independent) for reporting this issue.
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