Build Of KeycloakApplication · Redhat
CVE-2026-9704
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · uneditedA 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.
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysis · moderate confidenceIn Keycloak, an authenticated low-privilege user can send an oversized subject_token JWT (exceeding 4000 characters) to the TokenEndpoint. When the token exceeds the 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, resulting in privilege escalation.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.
NVD · CPE data
Build Of KeycloakApplication
all versionsCVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Network
- Complexity
- Low
- Privileges
- Low
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- High
- Availability
- High
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.
dbcve checksWork through these to decide whether this CVE applies to you.
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Identify Keycloak installationCheck if your environment runs Red Hat Build of Keycloak by reviewing installed software, container images, or service manifests. Look for Keycloak-related processes, containers, or services.Affected if Red Hat Build of Keycloak is present in the environment
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Verify TokenEndpoint exposureDetermine if the TokenEndpoint (/realms/{realm}/protocol/openid-connect/token) is accessible from network locations where low-privilege users can reach it. Review your reverse proxy and network access controls.Affected if TokenEndpoint is exposed to low-privilege users without additional restrictions
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Review logs for oversized token submissionsSearch Keycloak server logs for entries indicating oversized subject_token values (exceeding 4000 characters) submitted to the TokenEndpoint. Look for patterns like 'token too long', 'subject_token', or 'token dropped' in the logs.Affected if Logs show oversized subject_token submissions to the TokenEndpoint
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Audit for privilege escalation via token exchangeReview authentication and authorization logs for instances where low-privilege users suddenly acquired client service account permissions. Look for token exchange requests that resulted in elevated access rights.Affected if Low-privilege users have obtained service account permissions through the token endpoint
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Check for token exchange feature usageReview Keycloak configuration to determine if token exchange functionality is enabled or if clients are configured to allow subject_token-based exchanges. Examine client settings related to token exchange.Affected if Token exchange is enabled and accessible to low-privilege users
If you run Red Hat Build of Keycloak with an exposed TokenEndpoint and logs show oversized subject_token submissions resulting in privilege escalation, your environment is affected by this vulnerability.
Generated from the published advisory. Verify against your own configuration.
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
From vendor dataApply the vendor-supplied patch or update to a fixed version of Keycloak once available. Until then, monitor token endpoint logs for oversized token submissions and consider implementing additional access controls on service account permissions.
Fix this in Build Of Keycloak
Scoped from the published advisory
- Consultation4.0 h
- Implementation8.0 h
- Testing6.0 h
- Review / QA2.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $5,600.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2026-9704 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2026-9704 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- Verified mitigations, workarounds, and config changes
- Version or environment caveats, and links to real fixes
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