Oracle Essbase: Missing authentication allows unauthenticated takeover
Summary
Oracle Essbase 21.8.3.0.0 has a flaw in its Security component (CWE-287, CWE-306) that allows access without authentication. A remote attacker with TCP network access to the server can take over Essbase without credentials or user interaction. Oracle rates the impact as high for confidentiality, integrity and availability, with a CVSS base score of 9.8. Essbase servers should not be reachable from the internet.
Affected
- Oracle Essbase 21.8.3.0.0 (the only version listed in the CVE record and the October 2026 CPU)
Fixed in
- Oracle Critical Patch Update October 2026
- Patch ID and fixed version: Unknown, take both from Oracle's advisory
Workaround
- Unknown: no vendor workaround documented.
- Until patched, restrict network access to the Essbase server and limit which hosts can reach it.
Exploitation
- Not listed in CISA KEV in the sources reviewed (secondary sources only).
- No public proof-of-concept found.
- CISA SSVC: exploitation none, automatable yes, technical impact total.
Our recommendation
- Identify all Essbase servers, including planning/EPM deployments in finance or BI teams.
- Confirm the patch ID and fixed version in Oracle's October 2026 CPU advisory and apply the patch in the same cycle as the other Essbase patches.
- Block access to Essbase from the internet, VPNs and cloud networks until patched.
- Monitor for a public PoC or KEV addition.
Public exploits
PoC-in-GitHub, Metasploit and Exploit-DB list nothing for this CVE.
Research sources
- Oracle Security Alert: October 2026 CPU www.oracle.com
- OpenCVE: CVE-2026-91665 app.opencve.io
- TheHackerWire: CVE-2026-91665 www.thehackerwire.com
- Waratek: Oracle October 2026 Critical Patch Update waratek.com
- Vulners: CVE-2026-91665 vulners.com
Researched and written up in English and German by an AI (Claude by Anthropic) based on NVD, CISA, EPSS and the sources listed. The vendor information is authoritative. Researched on 30 Oct 2026, 17:08.
Original description (NVD)
Vulnerability in Oracle Essbase (component: Security). The supported version that is affected is 21.8.3.0.0. Easily exploitable vulnerability allows unauthenticated attacker with network access via TCP to compromise Oracle Essbase. Successful attacks of this vulnerability can result in takeover of Oracle Essbase. CVSS 3.1 Base Score 9.8 (Confidentiality, Integrity and Availability impacts). CVSS Vector: (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H).
NVD references (1)
Sources
The tracker combines official, freely usable data sources – updated continuously:
- NVD (NIST) – CVEs, rating (CVSS), affected products
- CISA KEV – vulnerabilities confirmed by CISA as actively exploited
- CISA Vulnrichment – CISA assessment (SSVC) in the official CVE record
- FIRST EPSS – probability of exploitation
- Microsoft MSRC – Patch Tuesday: vulnerabilities, severity, updates
- PoC-in-GitHub – public proof-of-concept repositories
- Metasploit (Rapid7) – modules of the Metasploit Framework
- Exploit-DB (OffSec) – archive of public exploits (links only)
- Patch days: official vendor pages (linked per vendor) (Vendor patch days)
This product uses data from the NVD API but is not endorsed or certified by the NVD. EPSS data © FIRST.org.
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