How severe is CVE-2026-91661?

CVE-2026-91661 has a CVSS score of 7.7/10, rated HIGH. Immediate patching is strongly recommended.

Which products are affected by CVE-2026-91661?

CVE-2026-91661 affects the following products: oracle essbase.

How do I patch CVE-2026-91661?

No patch has shipped for CVE-2026-91661 yet — track the oracle essbase advisory for a fixed release and apply the workarounds below in the meantime.

How do I detect CVE-2026-91661 across my infrastructure?

Inventory every oracle essbase deployment and check each version against the affected-products list above.

How do I mitigate CVE-2026-91661 if there is no patch (or I can't update yet)?

If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands. Alongside that, restrict the management interface to trusted networks and apply the vendor's recommended configuration mitigations.

Is CVE-2026-91661 actively exploited in the wild?

No public exploit code has been indexed for CVE-2026-91661 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2026-91661?

CVE-2026-91661 has an EPSS (Exploit Prediction Scoring System) score of 0.3%, placing it in the 22th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

Which products and versions are affected by CVE-2026-91661?

CVE-2026-91661 affects oracle essbase (1 version, e.g. 21.8.3.0.0). Check the affected-products list on this page against your deployed version to confirm exposure.

When was CVE-2026-91661 published, and has it been updated?

CVE-2026-91661 was published on October 20, 2026 and was last updated on October 23, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

🛡️

Not in CISA KEV

HIGH severity

CVE-2026-91661 — Essbase

HIGH

CVE-2026-91661 is a high-severity (CVSS 7.7) vulnerability in oracle essbase. No vendor fix is recorded yet; mitigation options are listed below.

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…

Published

Oct 20, 2026

Updated

Oct 23, 2026

Affected

1 product

Patched

See advisory

Exploits

None indexed

Exploitation data as of Oct 22, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗

0.3%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs22th percentile — riskier than 22% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

CVE-2026-91661 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.

Where this sits among everything scored

Of 394,415 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.

Description

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 unauthorized access to critical data or complete access to all Oracle Essbase accessible data. CVSS 3.1 Base Score 7.7 (Confidentiality impacts). CVSS Vector: (CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:N/A:N).

Affected Products

1 product · 1 configurations

Application

essbaseoracle

1 version

21.8.3.0.0

Detection & mitigation playbook

Vendor / appliance

Detect
Inventory every oracle essbase deployment and check each version against the affected-products list above.
Remediation status
No patch has shipped for CVE-2026-91661 yet — track the oracle essbase advisory for a fixed release and apply the workarounds below in the meantime.
Mitigate without a patch
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands. Alongside that, restrict the management interface to trusted networks and apply the vendor's recommended configuration mitigations.

Frequently Asked Questions

O3 Security · Runtime Protection

Is CVE-2026-91661 being exploited in your environment?

Detect and block the exploit chain at execution, on systems you cannot patch yet.

Protect my workloads How runtime protection works