CVE-2026-9704
Keycloak: keycloak: privilege escalation due to oversized subject_token jwt
Description
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.
INFO
Published Date :
May 27, 2026, 2:17 p.m.
Last Modified :
June 10, 2026, 10:17 p.m.
Remotely Exploit :
Yes !
Source :
[email protected]
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS 3.1 | MEDIUM | 53f830b8-0a3f-465b-8143-3b8a9948e749 | ||||
| CVSS 3.1 | MEDIUM | [email protected] | ||||
| CVSS 3.1 | MEDIUM | MITRE-CVE | ||||
| CVSS 3.1 | HIGH | [email protected] |
Solution
- Implement strict JWT size limits.
- Validate token contents before processing.
- Update Keycloak to the latest version.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-9704.
| URL | Resource |
|---|---|
| https://access.redhat.com/errata/RHSA-2026:25097 | |
| https://access.redhat.com/errata/RHSA-2026:25098 | |
| https://access.redhat.com/security/cve/CVE-2026-9704 | Mitigation Vendor Advisory |
| https://bugzilla.redhat.com/show_bug.cgi?id=2481877 | Issue Tracking Vendor Advisory |
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-9704 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-9704
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-9704 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-9704 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
-
CVE Modified by [email protected]
Jun. 10, 2026
Action Type Old Value New Value Added Reference https://access.redhat.com/errata/RHSA-2026:25097 -
CVE Modified by [email protected]
Jun. 10, 2026
Action Type Old Value New Value Added Reference https://access.redhat.com/errata/RHSA-2026:25098 -
Initial Analysis by [email protected]
Jun. 03, 2026
Action Type Old Value New Value Added CVSS V3.1 AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H Added CPE Configuration OR *cpe:2.3:a:redhat:build_of_keycloak:-:*:*:*:-:*:*:* Added Reference Type Red Hat, Inc.: https://access.redhat.com/security/cve/CVE-2026-9704 Types: Mitigation, Vendor Advisory Added Reference Type Red Hat, Inc.: https://bugzilla.redhat.com/show_bug.cgi?id=2481877 Types: Issue Tracking, Vendor Advisory -
New CVE Received by [email protected]
May. 27, 2026
Action Type Old Value New Value Added Description 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. Added CVSS V3.1 AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:N Added CWE CWE-1284 Added Reference https://access.redhat.com/security/cve/CVE-2026-9704 Added Reference https://bugzilla.redhat.com/show_bug.cgi?id=2481877