CVE-2026-97846

Keycloak provides a feature called mTLS holder-of-key binding which ensures that a token can only be used by the client that originally requested it by binding it to their digital certificate. A flaw was discovered where the new Standard Token Exchange V2 feature does not check for this certificate. This allows an attacker with stolen client credentials to obtain a standard, unrestricted token that bypasses these security protections.

The Red Hat Product Security team has assessed the severity of this vulnerability as Moderate, given that exploitation requires the attacker to already possess valid client credentials and a valid subject token, and requires specific non-default configurations. Successful exploitation allows an attacker to bypass mTLS sender-constraints and obtain unconstrained Bearer tokens. The vulnerability's root cause is a missing enforcement check for client certificates in the Standard Token Exchange V2 grant provider.

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.

Bugzilla 2540949 : keycloak-services: keycloak-services: Standard Token Exchange V2 bypasses mTLS holder-of-key binding

CWE-287 : Improper Authentication

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

cve.org: CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:N

Understanding the Weakness (CWE)

Integrity,Confidentiality,Availability,Access Control

Technical Impact: Read Application Data; Gain Privileges or Assume Identity; Execute Unauthorized Code or Commands

This weakness can lead to the exposure of resources or functionality to unintended actors, possibly providing attackers with sensitive information or even execute arbitrary code.

Frequently Asked Questions

"Under investigation" doesn't necessarily mean that the product is affected by this vulnerability. It only means that our Analysis Team is still working on determining whether the product is affected and how it is affected.

The term 'Affected' means that our Analysis team has determined that this product, such as Red Hat Enterprise Linux 8 or OpenShift Container Platform 4, is affected by this vulnerability and a fix may be released to address this issue in the near future. This includes all minor releases of this product unless noted otherwise in the Statement text.

Upgrade to a supported product version that includes a fix for this vulnerability (recommended).

Apply a mitigation (if one exists).

Customers with the Technical Account Manager (TAM) RHEL Security Select Add-on can review this CVE directly with their TAM.

Apply a mitigation (if one exists).

Red Hat Engineering focuses on addressing high-priority issues based on the impact and product lifecycle expectations. Therefore, lower-priority issues will not receive immediate fixes.

Customers with the technical account manager (TAM) RHEL Security Select Add-on can review this CVE directly with their TAM.

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