CVE-2026-73934Network attack vector

Denial of service via HTTP/2 window overflow

Published Aug 18, 2026 · Updated Aug 19, 2026

Denial of service in the Imperative Web Server in Oracle Helidon 3.2.19 allows remote attackers to crash the server via HTTP/2 settings. In HelidonConnectionHandler.onSettingsRead, the server accepted a client-supplied HTTP/2 initial window size and updated flow-control state without rejecting values that would overflow active stream windows; the fixing commit adds validateInitialWindowSize before acknowledging SETTINGS. Exposure requires unauthenticated network reachability to an HTTP/2 listener, and the published impact is limited to a hang or repeatable crash rather than data access or code execution.

CVSS severity7.5
High
EPSS probability0.31%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Denial of service in the Imperative Web Server in Oracle Helidon 3.2.19 allows remote attackers to crash the server via HTTP/2 settings. In HelidonConnectionHandler.onSettingsRead, the server accepted a client-supplied HTTP/2 initial window size and updated flow-control state without rejecting values that would overflow active stream windows; the fixing commit adds validateInitialWindowSize before acknowledging SETTINGS. Exposure requires unauthenticated network reachability to an HTTP/2 listener, and the published impact is limited to a hang or repeatable crash rather than data access or code execution.

The record

CVE
CVE-2026-73934
Published
Aug 18, 2026
Updated
Aug 19, 2026
Vendor
Oracle
Product
Helidon
Classifications
CWE-284, T1499
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Aug 18, 2026CVE publishedPublication date reported by the CVE source.
  2. Aug 19, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=3.2.19

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Oracle · Helidonversion=3.2.19

Published CVSS scores

7.5OracleCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-284Improper Access Control
T1499Endpoint Denial of Service

Public exploit references

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Technologies

Your stack

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Your stack

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