CVE-2026-78669Network attack vectorHinoki check available

CPU exhaustion via repeated initial-window updates

Published Oct 8, 2026 · Updated Oct 8, 2026

CPU exhaustion in Go standard library net/http before 1.26.9 allows remote attackers to degrade HTTP/2 clients or servers via SETTINGS frames. Initial-window handling performs work proportional to the number of streams for each SETTINGS_INITIAL_WINDOW_SIZE change, amplifying many small frames after many streams are opened. Exploitation requires an HTTP/2 peer connection; the reported consequence is excessive CPU consumption, not a documented crash or reboot.

CVSS severityUnavailable
Unscored
EPSS probability0.57%
Next 30 days · Oct 19, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkAvailable
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Summary

What happened

CPU exhaustion in Go standard library net/http before 1.26.9 allows remote attackers to degrade HTTP/2 clients or servers via SETTINGS frames. Initial-window handling performs work proportional to the number of streams for each SETTINGS_INITIAL_WINDOW_SIZE change, amplifying many small frames after many streams are opened. Exploitation requires an HTTP/2 peer connection; the reported consequence is excessive CPU consumption, not a documented crash or reboot.

The record

CVE
CVE-2026-78669
Published
Oct 8, 2026
Updated
Oct 8, 2026
Vendor
Go standard library
Product
net/http
Classifications
CWE-405, T1499
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Oct 8, 2026CVE publishedPublication date reported by the CVE source.
  2. Oct 8, 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=0 <1.26.9

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Go standard library · net/httpversion=0 <1.26.9
golang.org/x/net · golang.org/x/net/http2version=0 <0.60.0
Go standard library · net/http/internal/http2version=1.27.0-0 <1.27.2

Published CVSS scores

No CVSS assessment is available in this record.

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Activity data is delayed. The latest report is Sep 28, 2026.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 22, 2026Sep 28, 2026
Latest reporting daySep 28, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-405Asymmetric Resource Consumption (Amplification)
T1499Endpoint Denial of Service

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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