CVE-2025-9708Network attack vector

API traffic interception via permissive custom CA validation

Published Sep 16, 2025 · Updated Sep 16, 2025

Improper certificate validation in Kubernetes C# Client 17.0.13 and earlier allows man-in-the-middle attackers to read or alter API traffic. The custom-CA callback in Kubernetes.ConfigInit.cs adds the configured CA to ExtraStore and permits unknown-authority chain errors, allowing a valid certificate from another CA to pass. Exploitation requires a custom CA in kubeconfig and communication over an untrusted network; successful interception exposes API traffic and permits API-server impersonation.

CVSS severity6.8
Medium
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

Improper certificate validation in Kubernetes C# Client 17.0.13 and earlier allows man-in-the-middle attackers to read or alter API traffic. The custom-CA callback in Kubernetes.ConfigInit.cs adds the configured CA to ExtraStore and permits unknown-authority chain errors, allowing a valid certificate from another CA to pass. Exploitation requires a custom CA in kubeconfig and communication over an untrusted network; successful interception exposes API traffic and permits API-server impersonation.

The record

CVE
CVE-2025-9708
Published
Sep 16, 2025
Updated
Sep 16, 2025
Vendor
Kubernetes
Product
Kubernetes C# Client
Classifications
CWE-295, T1557
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Sep 16, 2025CVE publishedPublication date reported by the CVE source.
  2. Sep 16, 2025Record 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 <=17.0.13

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Kubernetes · Kubernetes C# Clientversion=0 <=17.0.13

Published CVSS scores

6.8KubernetesCVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:N

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.

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No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-295Improper Certificate Validation
T1557Adversary-in-the-Middle

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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