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CVE-2026-9704 medium CVSS 6.8

Vulnerability in org.keycloak:keycloak-server-spi-private (CVE-2026-9704)

Summary

Vulnerability in org.keycloak:keycloak-server-spi-private (CVE-2026-9704). Confidential information can be exposed externally. Mitigation: upgrade to 26.6.3 or later.

Original description

The description as published by the source.

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.

Source: NIST National Vulnerability Database NVD GitHub Advisory

Auto-generated summary

Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.

A vulnerability tracked as CVE-2026-9704 has been found in org.keycloak:keycloak-server-spi-private.
Confidential information can be exposed externally. CVSS score: 6.8/10.
What to do: upgrade org.keycloak:keycloak-server-spi-private to 26.6.3 or later.
If unsure, ask your IT team or search "org.keycloak:keycloak-server-spi-private CVE-2026-9704" on the vendor's site.

CVE-2026-9704 (org.keycloak:keycloak-server-spi-private) — CWE-1284 / CVSS v3 6.8
Attack vector: remote (network-reachable) / no user interaction
Patched: 26.6.3 — apply immediately
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.

❓ What is the problem

A vulnerability (CWE-1284) exists in org.keycloak:keycloak-server-spi-private.

📍 Affected scope

Check the vendor advisory for the affected versions of org.keycloak:keycloak-server-spi-private.

🔥 Severity

Severity: Medium (CVSS 6.8/10). Confidential information can be exposed externally.

🔧 How to fix

Update to 26.6.3.

🛡️ Workaround

Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.

🔍 Detection

Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Audit SBOM/dependencies to find affected services.

Response actions

Concrete steps and command examples for SOC/SRE teams to execute in order

  1. 1
    Identify exposure identify 
    Audit SBOM/dependencies for affected components.

    資産台帳・SBOM・依存マニフェストで org.keycloak:keycloak-server-spi-private を使っているサービスとバージョンを洗い出す。

  2. 2
    Apply patch patch 
    Upgrade org.keycloak:keycloak-server-spi-private to 26.6.3

    ステージング環境で 26.6.3 に上げて回帰テスト → 本番反映。回帰テストはアプリの主要ハッピーパスを含めること。

  3. 3
    Post-deployment verification verify 
    Confirm patched version is live in production

    パッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番ではアクセスログ・WAF でアラート再発が無いか継続監視。

Affected packages

maven org.keycloak:keycloak-server-spi-private
[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"26.6.3"}]}]
maven org.keycloak:keycloak-services
[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"26.6.3"}]}]

References

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