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CVE-2026-56853VulnerabilityPublished

Kubernetes: When a server is configured to support unencrypted HTTP/2, it reads a few bytes from each new connection

Affects kubernetesSource GCVE Database

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Authoritative record:CVE-2026-56853· High 7.5

Not known to be exploited · CVSS 7.5 High : upgrade to 1.34.13-r2 soon.

Data as of 11 Nov 2026, 03:39 UTC

CVSS 3.1 base score
7.5High
How severe the flaw is on the 0–10 CVSS scale.
Patch
Available – fixed in 1.34.13-r2, 4.1.6-r1
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 13 Aug 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 10 Nov 2026.

What to do

Upgrade kubernetes to 1.34.13-r2; argo-workflows to 4.1.6-r1.

Affected software

ProductAffectedFixed in
CleanStartkubernetespkg:apk/cleanstart/kubernetesOther threatsAffected
  • <1.34.13-r2
Fixed in
  • 1.34.13-r2
CleanStartargo-workflowspkg:apk/cleanstart/argo-workflowsOther threatsAffected
  • <4.1.6-r1
Fixed in
  • 4.1.6-r1

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

A patch is available and has been released in Kubernetes versions 1.34.13-r2 and 4.1.6-r1. Users should upgrade to these fixed versions to remediate the vulnerability. No additional mitigation actions are specified or required beyond applying the official fix.

Description

CVE-2026-56853 is a high-severity vulnerability affecting Kubernetes servers configured to support unencrypted HTTP/2. The issue involves the server reading a few bytes from each new connection to detect the HTTP/2 client preface, which can lead to an availability impact. Fixed versions 1.34.13-r2 and 4.1.6-r1 address this vulnerability.

References

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