Oracle Essbase: Authorization flaw allows full takeover via HTTP
Summary
Oracle Essbase 21.8.3.0.0 contains a flaw in its Security component (CWE-284, improper access control). An attacker with a low-privileged account and network access via HTTP can compromise the product, with impact that extends beyond Essbase itself (scope change). Oracle rates the issue 9.9 (Critical), and the advisory indicates no known exploitation at the time of publication.
Affected
- Oracle Essbase 21.8.3.0.0
- Earlier releases: Unknown.
Fixed in
- Fixed in the Oracle Critical Patch Update of October 2026. Exact patch identifier and fixed version number: Unknown. Check the Oracle advisory and My Oracle Support (Doc ID CPU289).
Workaround
- No vendor workaround known.
- Interim risk reduction (not vendor guidance): restrict HTTP access to Essbase to trusted internal networks and remove any internet exposure.
Exploitation
- Not listed in CISA KEV.
- CISA SSVC: exploitation none, not automatable.
- No public proof of concept found for this CVE.
- Oracle does not mention exploitation in its advisory.
Our recommendation
- Apply the October 2026 Oracle CPU patch for Essbase as a priority if the product is in use.
- Check whether Essbase is installed and whether its HTTP interface is reachable from outside the internal network.
- Review low-privileged accounts that can log in and remove unneeded ones.
- Patch sibling CVEs of the same CPU (e.g. CVE-2026-91637, CVE-2026-91658) together.
- If Essbase is not in use, confirm that it is not installed.
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
- Oracle Essbase 21.8.3 is now available blogs.oracle.com
- Oracle Security Blog: October 2026 CPU released blogs.oracle.com
- OpenCVE: CVE-2026-91638 app.opencve.io
- Waratek: Oracle October 2026 CPU waratek.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, 15:04.
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 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).
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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