CLEANSTART-2026-ZP29040: When a server is configured to support unencrypted HTTP/2, it reads a few bytes from each new connection to see if they contain the HTTP/2 client preface

Q: Which deployments are exposed to this issue?

The affected software listed is cleanstart/kubernetes and cleanstart/argo-workflows. Exposure requires the server to be configured to support unencrypted HTTP/2.

Q: Does exploitation require authentication or user interaction?

No. The supplied vector indicates network-based exploitation with low attack complexity, no privileges required, and no user interaction.

Q: What is the primary security impact?

The reported impact is availability only. Confidentiality and integrity impacts are listed as none, while availability impact is high.

Published Nov 11, 2026

Updated

CVE-2026-56853 affects multiple packages. When a server is configured to support unencrypted HTTP/2, it reads a few bytes from each new connection to see if they contain the HTTP/2 client preface. See references for individual vulnerability details.

Affected Software

2 affected componentsFixes available

cleanstart/kubernetes<1.34.13-r2

1.34.13-r2

cleanstart/argo-workflows<4.1.6-r1

4.1.6-r1

Remediation

Recommended actions to resolve this vulnerability, in priority order.

Upgrade
Upgrade cleanstart/kubernetes to a version that resolves this vulnerability.
Fixed in 1.34.13-r2
Upgrade
Upgrade cleanstart/argo-workflows to a version that resolves this vulnerability.
Fixed in 4.1.6-r1

Event History

Nov 11, 2026

Advisory Published

via OSV·12:40 AM

Data Sourced

via OSV·12:40 AM

DescriptionSeverityAffected Software

Child vulnerabilities

Contains the following vulnerabilities.

CVE-2026-56853

Frequently Asked Questions

Which deployments are exposed to this issue?

The affected software listed is cleanstart/kubernetes and cleanstart/argo-workflows. Exposure requires the server to be configured to support unencrypted HTTP/2.

Does exploitation require authentication or user interaction?

No. The supplied vector indicates network-based exploitation with low attack complexity, no privileges required, and no user interaction.

What is the primary security impact?

The reported impact is availability only. Confidentiality and integrity impacts are listed as none, while availability impact is high.

CLEANSTART-2026-ZP29040: When a server is configured to support unencrypted HTTP/2, it reads a few bytes from each new connection to see if they contain the HTTP/2 client preface

Affected Software

Remediation

Event History

Child vulnerabilities

Frequently Asked Questions

Which deployments are exposed to this issue?

Does exploitation require authentication or user interaction?

What is the primary security impact?

Company

Resources

Contact

Frequently Asked Questions

Which deployments are exposed to this issue?

Does exploitation require authentication or user interaction?

What is the primary security impact?