What is the CVSS score of CVE-2026-9704?

CVE-2026-9704 has a CVSS 3.1 base score of 8.8 (High). CVSS vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H. EPSS exploitation probability: 0.0%.

Which versions of Keycloak are affected by CVE-2026-9704?

Red Hat Build of Keycloak contains a privilege escalation vulnerability (CVE-2026-9704) allowing authenticated users to assume the permissions of critical service accounts, creating a direct pathway…. A patch is available.

How to fix or mitigate CVE-2026-9704?

Within 24 hours: Complete inventory of all Red Hat Build of Keycloak deployments, identify which service accounts have elevated privileges and their downstream system dependencies, and document current authentication flows. Within 7 days: Implement network-level or WAF controls to reject JWT tokens exceeding 4000 characters at the TokenEndpoint, enable detailed audit logging for all TokenEndpoint authentication attempts, and conduct least-privilege review of all active service account permissions. Within 30 days: Monitor Red Hat security advisories for patch availability; upon release, validate the patch in non-production environment and schedule deployment through standard change management.

Keycloak CVE-2026-9704

EUVD-2026-32300 HIGH

Improper Validation of Specified Quantity in Input (CWE-1284)

2026-05-27 secalert@redhat.com

GHSA-rr5q-3xwr-f323

Privilege Escalation Build Of Keycloak

8.8

CVSS 3.1 · NVD

Severity by source

NVD PRIMARY

8.8 HIGH

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

vuln.today AI

8.8 HIGH

Remote token endpoint (AV:N), trivial oversized-JWT trick (AC:L), requires a low-privileged account (PR:L), no user interaction; escalation to service account yields full CIA within the realm.

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

4.0 AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N

Red Hat

6.8 MEDIUM

qualitative

Primary rating from NVD.

CVSS VectorNVD

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

Attack Vector

Network

Attack Complexity

Low

Privileges Required

Low

User Interaction

None

Scope

Unchanged

Confidentiality

High

Integrity

High

Availability

High

Lifecycle Timeline

Analysis Updated

Jun 10, 2026 - 22:34 vuln.today

v3 (cvss_changed)

Analysis Updated

Jun 10, 2026 - 22:33 vuln.today

v2 (cvss_changed)

Re-analysis Queued

Jun 10, 2026 - 22:22 vuln.today

cvss_changed

Severity Changed

Jun 10, 2026 - 22:22 NVD

MEDIUM HIGH

CVSS changed

Jun 10, 2026 - 22:22 NVD

6.8 (MEDIUM) 8.8 (HIGH)

Analysis Generated

May 27, 2026 - 21:17 vuln.today

Blast Radius

ecosystem impact

† from your stack dependencies † transitive graph · vuln.today resolves 4-path depth

81 maven packages depend on org.keycloak:keycloak-server-spi-private (45 direct, 36 indirect)
70 maven packages depend on org.keycloak:keycloak-services (36 direct, 34 indirect)

Ecosystem-wide dependent count for version 26.6.3 and other introduced versions.

DescriptionNVD

A flaw was found in Keycloak. An authenticated user with low privileges can exploit this vulnerability by sending an oversized subject_token JSON Web Token (JWT) to the TokenEndpoint. When the token exceeds a 4000-character limit, it is silently dropped, causing the system to fall back to client credentials. This allows the user to gain the permissions of the client's service account, leading to privilege escalation.

AnalysisAI

Privilege escalation in Red Hat Build of Keycloak allows low-privileged authenticated users to assume the permissions of a client's service account by submitting an oversized subject_token JWT to the TokenEndpoint. When the token exceeds the 4000-character limit it is silently discarded rather than rejected, causing the server to fall back to client-credentials authentication and grant the attacker the client's service-account scope. No public exploit identified at time of analysis and EPSS is very low (0.04%), but CVSS rates the issue 8.8 due to full CIA impact post-exploitation.

Technical ContextAI

Keycloak is Red Hat's open-source identity and access management server implementing OAuth 2.0, OIDC, and SAML, with the affected component being the OAuth2 TokenEndpoint that handles token exchange and grant processing. The root cause maps to CWE-1284 (Improper Validation of Specified Quantity in Input): the endpoint enforces a 4000-character ceiling on the subject_token parameter but, instead of returning an error when the limit is exceeded, silently drops the token and continues processing the request. Because token exchange requests typically also carry client credentials, the server then authenticates the request as the client itself and issues a token bound to the client's service account rather than the original subject - effectively converting a malformed delegation request into a successful client-credentials grant. The CPE confirms the impact applies to cpe:2.3:a:redhat:build_of_keycloak (Red Hat's hardened distribution of upstream Keycloak).

RemediationAI

Patch available per vendor advisory: apply the updates shipped in RHSA-2026:25097 (https://access.redhat.com/errata/RHSA-2026:25097) and RHSA-2026:25098 (https://access.redhat.com/errata/RHSA-2026:25098), which correspond to the patched Red Hat Build of Keycloak releases; exact fix version numbers should be confirmed against the linked errata for your specific Keycloak stream. Until patching is complete, compensating controls include disabling the token-exchange feature on clients that do not require it (this breaks any delegation flows that rely on subject_token swap), restricting which clients are permitted to perform token exchange via the fine-grained admin permission model, tightly scoping each client's service-account roles to the minimum necessary so a fallback to client credentials does not yield administrative permissions, and adding a reverse-proxy or WAF rule that rejects token-endpoint requests whose subject_token parameter exceeds ~4000 characters (trade-off: legitimate large JWTs with many claims may be blocked). Monitor Keycloak audit logs for token-exchange requests that result in client-credentials grants from accounts that previously used a subject_token.