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CVE-2026-73921 – Unauthenticated RCE / Full Server Takeover – Oracle Helidon 1.4.20 (Imperative Web

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Summary

CVE-2026-73921 is a critical vulnerability affecting the Imperative Web Server component of Oracle Helidon. It allows an unauthenticated, remote attacker with network access via HTTP to fully compromise the affected Helidon server, with impacts to confidentiality, integrity, and availability. Oracle rates the flaw as easily exploitable and requiring no privileges or user interaction, resulting in a CVSS v3.1 base score of 9.8 (Critical).

Technical details

  • Root cause: A flaw in the Imperative Web Server component of Oracle Helidon that permits an attacker to take over the affected server process; the official Oracle CVE record does not disclose deeper implementation-level root-cause detail (e.g., specific code path or CWE classification) beyond confirming the takeover impact.
  • Trigger conditions: Exploitable remotely over HTTP without authentication and without any user interaction.
  • Attack vector: Network (AV:N) — attack complexity is Low (AC:L), no privileges required (PR:N), no user interaction (UI:N).
  • Impact: Successful exploitation can result in complete takeover of the Helidon server, with high impact to confidentiality, integrity, and availability (C:H/I:H/A:H).

Affected software

  • Oracle Helidon, Imperative Web Server component — version 1.4.20

Severity

  • CVSS v3.1 Base Score: 9.8 (Critical)
  • Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Mitigation and recommended actions

  • Immediate: Apply the patch provided in Oracle’s August 2026 Critical Security Patch Update (CSPU) advisory. Organizations running Oracle Helidon should consult the CSPU August 2026 advisory to identify the fixed release for their deployed Helidon version and upgrade from 1.4.20 as directed by Oracle.
  • If immediate patching is not possible: Restrict network exposure of Helidon-based services (e.g., place them behind a firewall, VPN, or WAF and limit access to trusted networks only) until the patch can be applied, since the vulnerability is remotely exploitable over HTTP with no authentication required.
  • Monitor affected servers for anomalous HTTP traffic patterns as an interim detection measure while patching is planned.

References

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