---
id: "CVE-2026-91658"
kind: "vulnerability"
aliases: ["CVE-2026-91658"]
title: "Oracle Essbase: low-privileged HTTP user can take over the server"
severity: "critical"
cvss: 9.9
epss: 0.00286
exploited: false
status: "open"
category: "vendor"
products: [{"name": "oracle essbase", "fixed": [], "affected": "= 21.8.3.0.0", "ecosystem": "vendor"}, {"name": "essbase", "fixed": [], "affected": "= 21.8.3.0.0", "ecosystem": "vendor"}]
ecosystems: ["vendor"]
tags: ["enterprise-analytics", "oracle-essbase", "self-hosted", "vendor"]
not_affected_if: ["managed-hosting", "no-http-exposure", "other-versions"]
published_at: "2026-10-20T22:21:06+00:00"
first_seen_at: "2026-10-23T21:57:27+00:00"
updated_at: "2026-10-24T13:15:55+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-91658", "first_seen_at": "2026-10-23T21:57:27+00:00"}, {"source": "analyst", "url": null, "first_seen_at": "2026-10-23T22:54:03+00:00"}, {"source": "epss", "url": "https://api.first.org/data/v1/epss?cve=CVE-2026-91658", "first_seen_at": "2026-10-24T13:15:55+00:00"}]
---

# Oracle Essbase: low-privileged HTTP user can take over the server

Oracle Essbase 21.8.3.0.0 has a flaw in the Security component. A low-privileged user with HTTP access can take over Essbase, and the impact can reach other products in the environment (scope change, CVSS 9.9). Oracle fixed it in the October 2026 Critical Patch Update, which carries 38 Essbase fixes. No exploitation or public PoC is known.

_Summary, check and fix written by a model from the sources; labelled as such._

## Affected

- vendor:oracle essbase affected = 21.8.3.0.0 fixed ?
- vendor:essbase affected = 21.8.3.0.0 fixed ?

## How to check

Check your Essbase release: 21.8.3.0.0 is the affected version. Then confirm the October 2026 CPU Essbase patch is installed (see the patch availability document on My Oracle Support). Check whether Essbase HTTP is reachable by untrusted users, since any low-privileged account is enough.

## Fix

Apply the Oracle October 2026 CPU patch for Essbase from My Oracle Support (linked from cpuoct2026). Oracle's public pages give no new version string. Until patched, restrict Essbase HTTP access to trusted networks and review low-privileged accounts. Patch together with the other Essbase CPU fixes.

## Timeline

- 2026-10-23T21:57:27+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-91658
- 2026-10-23T22:54:03+00:00 analyst — Oracle Oct 2026 CPU (cpuoct2026) lists Essbase 21.8.3.0.0 affected, CVSS 9.9 (AV:N/PR:L/S:C), fixed via CPU patch; no fixed version string or patch number in pages read (MOS patch availability doc not opened). No exploitation or PoC found; X/Bluesky not searched.
- 2026-10-24T13:15:55+00:00 epss https://api.first.org/data/v1/epss?cve=CVE-2026-91658

## Documents

- [advisory] Oracle Critical Patch Update Advisory - October 2026 https://www.oracle.com/security-alerts/cpuoct2026.html
- [advisory] Text Form of Oracle CPU October 2026 Risk Matrices https://www.oracle.com/security-alerts/cpuoct2026verbose.html
- [describes] CVE Record: CVE-2026-91658 https://www.cve.org/CVERecord?id=CVE-2026-91658

## From the sources

Vulnerability in Oracle Essbase (component: Security).   The supported version that is affected is 21.8.3.0.0. Easily exploitable vulnerability allows low privileged attacker with network access via HTTP to compromise Oracle Essbase.  While the vulnerability is in Oracle Essbase, attacks may significantly impact additional products (scope change).  Successful attacks of this vulnerability can result in takeover of Oracle Essbase. CVSS 3.1 Base Score 9.9 (Confidentiality, Integrity and Availability impacts).  CVSS Vector: (CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H).

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_Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai_