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CVE-2026-73866 – Unauthenticated Data Manipulation via HTTP – Oracle Helidon 4.5.0 (Imperative Web S

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Summary

CVE-2026-73866 is a critical, easily exploitable vulnerability in the Imperative Web Server component of Oracle Helidon (part of Oracle Fusion Middleware). It allows an unauthenticated attacker with network access via HTTP to compromise Helidon, potentially leading to unauthorized creation, deletion, or modification of critical data and unauthorized access to all Helidon-accessible data. The flaw carries a CVSS v3.1 base score of 9.1 (Critical) and was disclosed by Oracle as part of its August 2026 Critical Security Patch Update.

Technical details

  • Root cause: A flaw in Helidon’s Imperative Web Server component that permits an attacker to bypass expected access controls when handling HTTP requests, as documented in Oracle’s official advisory.
  • Trigger conditions: No authentication or user interaction is required; the vulnerability is reachable by any party that can send HTTP requests to an exposed Helidon Imperative Web Server instance (Attack Complexity: Low).
  • Attack vector: Network (AV:N) over HTTP — Oracle explicitly notes this vulnerability "may be remotely exploitable without authentication."
  • Impact: High confidentiality impact (unauthorized read access to critical/all Helidon-accessible data) and high integrity impact (unauthorized creation, deletion, or modification of data), with no impact on availability.

Affected software

  • Oracle Helidon, version 4.5.0 (Imperative Web Server component)
  • Note: Oracle’s August 2026 Critical Security Patch Update addresses multiple related Helidon vulnerabilities across several release lines (1.4.19, 1.4.20, 3.2.18, 3.2.19, 3.2.20, 4.5.0, 4.5.1, 4.5.3); CVE-2026-73866 specifically affects the 4.5.0 release.

Severity

  • CVSS v3.1 Base Score: 9.1 (Critical)
  • Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

Mitigation and recommended actions

  • Immediate: Apply the Oracle August 2026 Critical Security Patch Update for Helidon and upgrade to a version beyond the affected 4.5.0 release, per the patch availability guidance referenced in Oracle’s advisory (My Oracle Support document referenced under the Fusion Middleware appendix, KB924578).
  • If patching cannot be performed immediately: Restrict network exposure of Helidon-based Imperative Web Server endpoints (e.g., place behind a firewall, VPN, or reverse proxy that limits access to trusted sources only) until the patch can be applied, since the vulnerability is exploitable over the network without authentication.
  • Oracle strongly recommends applying the Critical Security Patch Update as soon as possible, as the vulnerability is easily exploitable and requires no privileges or user interaction.

References

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