CVE-2021-25740: K8s.io/kubernetes Confused Deputy Vulnerability

LOW
Advisory Identifier: GHSA-vw47-mr44-3jf9
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CVSS 3.1
CWE-441 CWE-610
Published
Advisory Summary

CVE-2021-25740 is a LOW (CVSS 3.1) confused deputy vulnerability (CWE-441: Unintended Proxy or Intermediary ('Confused Deputy')) affecting K8s.io/kubernetes libraries in the Go ecosystem. The issue involves confused deputy in kubernetes. Remediation is available in the latest vendor maintenance releases.

CVE-2021-25740 at a Glance

CVE Identifier CVE-2021-25740
GHSA Identifier GHSA-vw47-mr44-3jf9
Severity LOW
CVSS v3.1 Base Score 3.1
CWE Classification CWE-441: Unintended Proxy or Intermediary ('Confused Deputy')
Affected Product K8s.io/kubernetes
Package Ecosystem Go
Published Date
Last Updated

Security Impact

CVSS: 3.1

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:L/I:N/A:N).

Attack Vector Network (AV:N)
Attack Complexity High (AC:H)
Privileges Required Low (PR:L)
User Interaction None (UI:N)
Scope Unchanged (S:U)
Confidentiality Low (C:L)
Integrity None (I:N)
Availability None (A:N)

How to Fix CVE-2021-25740

To remediate this vulnerability, upgrade all affected K8s.io/kubernetes dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

k8s.io/kubernetes fixed: Latest secure release 
Upgrade k8s.io/kubernetes to Latest secure release
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

inspect dependencies for k8s.io/kubernetes

How to Check if You Are Affected

To determine whether your application is affected by CVE-2021-25740, inspect your project dependencies for K8s.io/kubernetes:

inspect dependencies for k8s.io/kubernetes

Analyze the terminal output to locate any version of K8s.io/kubernetes in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than the patched release), your application is affected.

Note: Verify declared build manifests and deployed runtime container environments.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-441: Unintended Proxy or Intermediary ('Confused Deputy'), where the product receives a request, message, or directive from an upstream component, but the product does not sufficiently preserve the original source of the request before forwarding the request to an external actor that is outside of the product's control sphere. this causes the product to appear to be the source of the request, leading it to act as a proxy or other intermediary between the upstream component and the external actor. In K8s.io/kubernetes, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

A security issue was discovered with Kubernetes that could enable users to send network traffic to locations they would otherwise not have access to via a confused deputy attack.

CVE-2021-25740 Affected K8s.io/kubernetes Versions

1 component(s)
Product / Package Ecosystem Affected Versions Fixed Version
k8s.io/kubernetes
golang/k8s.io/kubernetes
Go
≤ 1.22.2

References

NVD — CVE-2021-25740 NVD
https://nvd.nist.gov/vuln/detail/CVE-2021-25740
K8s.io/kubernetes Source Repository REPOSITORY
https://github.com/kubernetes/kubernetes/issues/103675
K8s.io/kubernetes Source Repository REPOSITORY
https://github.com/kubernetes/kubernetes
K8s.io/kubernetes Security Information SECURITY
https://groups.google.com/g/kubernetes-security-announce/c/WYE9ptrhSLE
kubernetes.io/blog/2026/05/26/rec... WEB
https://kubernetes.io/blog/2026/05/26/reconciling-unfixed-kubernetes-cves
K8s.io/kubernetes Security Information SECURITY
https://security.netapp.com/advisory/ntap-20211014-0001

Frequently Asked Questions

What is CVE-2021-25740?
CVE-2021-25740 is a security vulnerability in K8s.io/kubernetes involving Confused Deputy in Kubernetes under CWE-441: Unintended Proxy or Intermediary ('Confused Deputy').
Which K8s.io/kubernetes versions are affected?
Affected versions include releases prior to current release patches across affected packages: k8s.io/kubernetes.
What version fixes CVE-2021-25740?
Upgrading to current release patches (or the latest patched release for your respective branch) resolves the vulnerability.
Is k8s.io/kubernetes affected?
Yes, k8s.io/kubernetes is affected in releases prior to Latest secure release. Upgrade your dependency to Latest secure release or later.
What is the CVSS score of CVE-2021-25740?
CVE-2021-25740 has a CVSS v3.1 base score of 3.1 (LOW) with vector string CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:L/I:N/A:N.
What CWE is associated with CVE-2021-25740?
CVE-2021-25740 is classified under CWE-441: Unintended Proxy or Intermediary ('Confused Deputy') (The product receives a request, message, or directive from an upstream component, but the product does not sufficiently preserve the original source of the request before forwarding the request to an external actor that is outside of the product's control sphere. This causes the product to appear to be the source of the request, leading it to act as a proxy or other intermediary between the upstream component and the external actor.).
How can I check Go dependencies for CVE-2021-25740?
Run the dependency tree command: 'inspect dependencies for k8s.io/kubernetes'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-vw47-mr44-3jf9",
  "modified" : "2026-06-09T10:51:38Z",
  "published" : "2021-09-21T18:28:30Z",
  "aliases" : [ "CVE-2021-25740" ],
  "summary" : "Confused Deputy in Kubernetes",
  "details" : "A security issue was discovered with Kubernetes that could enable users to send network traffic to locations they would otherwise not have access to via a confused deputy attack.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:L/I:N/A:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Go",
      "name" : "k8s.io/kubernetes"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "last_affected" : "1.22.2"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2021-25740"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/kubernetes/kubernetes/issues/103675"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/kubernetes/kubernetes"
  }, {
    "type" : "WEB",
    "url" : "https://groups.google.com/g/kubernetes-security-announce/c/WYE9ptrhSLE"
  }, {
    "type" : "WEB",
    "url" : "https://kubernetes.io/blog/2026/05/26/reconciling-unfixed-kubernetes-cves"
  }, {
    "type" : "WEB",
    "url" : "https://security.netapp.com/advisory/ntap-20211014-0001"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-441", "CWE-610" ],
    "severity" : "LOW",
    "github_reviewed" : true,
    "github_reviewed_at" : "2021-09-21T14:54:49Z",
    "nvd_published_at" : "2021-09-20T17:15:00Z"
  }
}