CVE-2026-73866: Vulnerability in the Helidon product of Oracle Fusion Middleware (component: Imperative Web Server)

This month

CRITICAL 9.1REMOTEDOWNGRADE

CVE-2026-73866 is a critical-severity flaw (CVSS 9.1) affecting helidon. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Vulnerability in the Helidon product of Oracle Fusion Middleware (component: Imperative Web Server). Supported versions that are affected are 4.0.0-4.4.1. Easily exploitable vulnerability allows unauthenticated attacker with network access via HTTP to compromise Helidon. Successful attacks of this vulnerability can result in unauthorized creation, deletion or modification access to critical data or all Helidon accessible data as well as unaut

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	9.1 (Critical)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.4% (top 64%)
CISA exploited list	No
Weakness	CWE-284
Published	2026-08-18
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

2026-08-18Published CVE record published
2026-10-22 17:09 UTCUpdated Record last modified

oracle helidon DOWNGRADE

Affected: 4.5.0

Fixed in: no fixed release known

Safe to downgrade to: a release before 4.5.0

1. Check installed version

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

2. No fixed release: DOWNGRADE to a release before 4.5.0 (Debian / Ubuntu)

apt-cache madison helidon sudo apt install helidon=<VERSION_BEFORE_4.5.0> sudo apt-mark hold helidon

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

dnf --showduplicates list helidon sudo dnf downgrade helidon-<VERSION_BEFORE_4.5.0> sudo dnf versionlock add helidon

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 · uv · FIXED · 0.13.5-1.fc46 · FEDORA-2026-61ea5a28c6 · source

sudo dnf upgrade --advisory=FEDORA-2026-61ea5a28c6

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-2026-73866?

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

Is CVE-2026-73866 being exploited?

CVE-2026-73866 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-2026-73866 affect?

CVE-2026-73866 affects helidon. Severity is critical (CVSS 9.1). Vulnerability in the Helidon product of Oracle Fusion Middleware (component: Imperative Web Server). Supported versions that are affected are 4.0.0-4.4.1. Easily exploitable vulnerability allows unauthenticated attacker with network access

How urgent is CVE-2026-73866?

Priority 49/100. Critical severity; CISA SSVC: automatable with total technical impact; Remotely exploitable, no login, no user action

Related CVEs

CVE-2026-60853 LOW 3.7 DOWNGRADE Vulnerability in the Helidon product of Oracle Fusion Middleware (component: Imperative Web Server)
CVE-2026-60915 HIGH 7.4 DOWNGRADE Vulnerability in the Helidon product of Oracle Fusion Middleware (component: Imperative Web Server)
CVE-2026-71074 CRITICAL 9.8 DOWNGRADE Vulnerability in the Helidon product of Oracle Fusion Middleware (component: Imperative Web Server)
CVE-2026-71152 CRITICAL 9.8 DOWNGRADE Vulnerability in the Helidon product of Oracle Fusion Middleware (component: Imperative Web Server)
CVE-2026-71164 CRITICAL 9.8 DOWNGRADE Vulnerability in the Helidon product of Oracle Fusion Middleware (component: Imperative Web Server)

References

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