High

CVE-2026-9704 — Keycloak: keycloak: privilege escalation due to oversized subject_token jwt

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.

Published May 27, 2026 · Updated Oct 13, 2026 · Sources: NIST National Vulnerability Database, CVE Program (cve.org) e CISA ADP · CNA: redhat

Low

Who exploits it and how urgent it is

A 0–100 score combining confirmed exploitation, ransomware and APT use, public exploits, EPSS and severity.

No exploitation signal in the sources consulted so far.

How the score was calculated

EPSS 0.6% (30-day exploitation probability)+7
Technical severity (high)+6

The score orders the patch queue; it does not replace your asset context (internet exposure, criticality, compensating controls).

Triage

Is it exploited, how likely is exploitation, what does it touch, and how severe do the sources call it.

Exploitation

Not confirmed

Not in CISA KEV — an absence of record, not proof it is unexploited.

EPSS FIRST

0.59%

ahead of 47% of scored CVEs · Oct 14, 2026

Affects

Red Hat

Build Of Keycloak and 2 more

CVSS base

8.8

High · 3 source(s)

CISA SSVC assessment CISA

Three decision points CISA publishes for the CVEs it assesses (SSVC 2.0.3). A stakeholder decision, not a severity score.

Exploitation

None

none · proof-of-concept · active

Automatable

can an attacker script the kill-chain steps

Technical impact

Total

partial · total control of the vulnerable component

Remediation

Fixes and mitigations documented by the sources — linked to the original advisory.

Documented mitigation — access.redhat.com (NIST National Vulnerability Database)

First 24 hours

Ordered from the record’s own fields — exposure first, because you cannot patch what you have not found. A rule-generated starting point.

Identify exposed assets running the affected vendor/product/version combinations (Red Hat Build Of Keycloak, Red Hat Red Hat build of Keycloak 26.4, Red Hat Red Hat build of Keycloak 26.6).
Apply the documented mitigations until a definitive fix is available.
Search available logs for exploit probes, errors and authentication anomalies.

Affected scope

Vendor, product and versions as the sources word them.

Vendor	Product	Versions	Status	Source
Red Hat	Build Of Keycloak	versions not specified by the source	Vulnerable	NIST National Vulnerability Database
Red Hat	Red Hat build of Keycloak 26.4	versions not specified by the source	Vulnerable	CVE Program (cve.org) e CISA ADP
Red Hat	Red Hat build of Keycloak 26.6	versions not specified by the source	Vulnerable	CVE Program (cve.org) e CISA ADP

Attack characteristics

The CVSS vector, decoded. It describes the attack, not your exposure to it.

Attack vector

Network

Attack complexity

Low

Privileges required

Low

User interaction

None

Scope

Unchanged

Confidentiality

High

Integrity

High

Availability

High

Every base score collected

Sources score independently and may disagree; each row says who scored it and under which version.

Score	Version	Severity	Expl.	Impact	Scored by
8.8	CVSS 3.1	High	2.8	5.9	nvd@nist.gov via NIST National Vulnerability Database
6.8	CVSS 3.1	Medium	1.6	5.2	secalert@redhat.com via NIST National Vulnerability Database
6.8	CVSS 3.1	Medium	—	—	redhat via CVE Program (cve.org) e CISA ADP

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H (score shown at the top: nvd@nist.gov)

Scoring entities (NIST, CNA, ADP) score independently; each score is shown with its origin. For prioritization we use 8.8 (NVD (NIST)) as a conservative provisional reference — not a definitive official score.

Weakness MITRE

Weakness class according to MITRE’s CWE catalog.

CWE-1284

Other CVEs with this weakness →

EPSS over time FIRST

Oct 13, 2026 → Oct 14, 2026 · 2 reading(s) · max 0.59%

Detection

Read off the CVSS vector and the weakness class. Starting points, not tested rules.

Prioritize edge telemetry for the network-reachable component (proxy, WAF, IDS/IPS).

web/proxy/WAF logsnetwork IDS/IPS

Timeline

What happened to this CVE, newest first.

2026
Affected products added · red hat/red hat build of keycloak 26.4, red hat/red hat build of keycloak 26.6
Oct 13, 2026 · CVE Program (cve.org) e CISA ADP
SSVC assessment updated
Oct 13, 2026 · CVE Program (cve.org) e CISA ADP
Record published
Oct 13, 2026
Fix documented
Oct 13, 2026 · NIST National Vulnerability Database
CVSS changed · 8.8
Oct 13, 2026 · NIST National Vulnerability Database
Source status changed · → Modified
Oct 13, 2026 · NIST National Vulnerability Database
Record created in this database
Oct 13, 2026 · NIST National Vulnerability Database
CVE published
May 27, 2026 · redhat

Source activity

Repeated readings are counted rather than listed.

1× Official description updated · Oct 13, 2026 – Oct 13, 2026

References

6 on the record

bugzilla.redhat.com/show_bug.cgi
Issue Tracking, Vendor Advisory, issue-tracking, x_refsource_REDHAT, NIST National Vulnerability Database
access.redhat.com/security/cve/CVE-2026-9704
Mitigation, Vendor Advisory, vdb-entry, x_refsource_REDHAT, NIST National Vulnerability Database
access.redhat.com/errata/RHSA-2026:25098
vendor-advisory, x_refsource_REDHAT, NIST National Vulnerability Database
access.redhat.com/errata/RHSA-2026:30050
vendor-advisory, x_refsource_REDHAT, NIST National Vulnerability Database
access.redhat.com/errata/RHSA-2026:25097
vendor-advisory, x_refsource_REDHAT, NIST National Vulnerability Database
access.redhat.com/errata/RHSA-2026:30049
vendor-advisory, x_refsource_REDHAT, NIST National Vulnerability Database

Elsewhere on this site

Red Hat
every CVE for this vendor

CWE-1284
other pages naming this weakness

Related CVEs (same products)

Medium CVE-2026-109082 Keycloak-services: keycloak-services: ciba confidential-only contract not enforced for public clients 3d
Medium CVE-2026-107889 Keycloak-services: keycloak-services: stored xss on login page via kcsanitize bypass 6d
Medium CVE-2026-107623 Keycloak-services: keycloak-services: oidc dcr read-modify-write silently disables offline token revocation 7d
Medium CVE-2026-107604 Keycloak-services: keycloak-services: view-clients role allows retrieval of active client secrets via installation provider endpoints 7d
Medium CVE-2026-107121 Keycloak-services: keycloak-services: smtp starttls plaintext credential and message downgrade 8d
Medium CVE-2026-105305 Keycloak-services: keycloak-services: device authorization grant bypasses per-client minimum.acr.value enforcement 9d

Not in any source we poll

Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.

No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
No exploit packet captures, log samples, or incident case IDs supplied.

Answered from this record

Text assembled only from the fields above — no additional claims.

What should defenders know first?

CVE-2026-9704 is "Keycloak: keycloak: privilege escalation due to oversized subject_token jwt", rated High. It affects Build Of Keycloak (Red Hat); versions are in the scope table. It is not in CISA KEV, which does not rule out exploitation. CVSS 8.8 describes technical severity. EPSS 0.59% estimates the probability of exploitation in 30 days; neither replaces your asset context. First verify whether exposed or business-critical assets run the affected versions, apply vendor fixes or mitigations, and preserve logs for review.

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