CVE-2026-91665: Vulnerability in Oracle Essbase (component: Security)

This month

CRITICAL 9.8REMOTEDOWNGRADE

CVE-2026-91665 is a critical-severity flaw (CVSS 9.8) affecting essbase. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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

Why this priority

Critical severity
CISA SSVC: automatable with total technical impact
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	9.8 (Critical)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.4% (top 66%)
CISA exploited list	No
Weakness	CWE-287, CWE-306
Published	2026-10-20
Last modified	2026-10-22

Publisher (CNA): Oracle · Vendor: oracle

Last updated 2026-10-22 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-10-20Published CVE record published
2026-10-22 23:20 UTCUpdated Record last modified

oracle essbase DOWNGRADE

Affected: 21.8.3.0.0

Fixed in: no fixed release known

Safe to downgrade to: a release before 21.8.3.0.0

1. Check installed version

apt-cache policy essbase || rpm -q essbase || essbase --version

2. No fixed release: DOWNGRADE to a release before 21.8.3.0.0 (Debian / Ubuntu)

apt-cache madison essbase sudo apt install essbase=<VERSION_BEFORE_21.8.3.0.0> sudo apt-mark hold essbase

2. No fixed release: DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list essbase sudo dnf downgrade essbase-<VERSION_BEFORE_21.8.3.0.0> sudo dnf versionlock add essbase

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

Exact fixes by distribution

A distro patch exists: prefer upgrading over downgrading.

Fedora 46 · python-streamlink · FIXED · 8.6.2-1.fc46 · FEDORA-2026-a56fcfdc08 · source

sudo dnf upgrade --advisory=FEDORA-2026-a56fcfdc08

Fedora ELN · valgrind · FIXED · 3.28.0-1.eln159 · FEDORA-2026-c593ef1d15 · source

sudo dnf upgrade --advisory=FEDORA-2026-c593ef1d15

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-91665?

essbase: downgrade or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2026-91665 being exploited?

CVE-2026-91665 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-91665 affect?

CVE-2026-91665 affects essbase. Severity is critical (CVSS 9.8). 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. Succe

How urgent is CVE-2026-91665?

Priority 51/100. Critical severity; CISA SSVC: automatable with total technical impact; Remotely exploitable, no login, no user action

Related CVEs

CVE-2026-91630 MEDIUM 6.8 DOWNGRADE Vulnerability in Oracle Essbase (component: Security)
CVE-2026-91631 MEDIUM 5.0 DOWNGRADE Vulnerability in Oracle Essbase (component: Security)
CVE-2026-91633 MEDIUM 6.0 DOWNGRADE Vulnerability in Oracle Essbase (component: Security)
CVE-2026-91634 MEDIUM 5.3 DOWNGRADE Vulnerability in Oracle Essbase (component: Security)
CVE-2026-91635 HIGH 8.1 DOWNGRADE Vulnerability in Oracle Essbase (component: Security)

References

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