# Unpatchable Vulnerabilities of Kubernetes: CVE-2021-25740

DevFeed: [Unpatchable Vulnerabilities of Kubernetes: CVE-2021-25740](<https://devfeed.tech/articles/unpatchable-vulnerabilities-of-kubernetes-cve-2021-25740-8300.md>)

Original publisher: [Read original article](<https://securitylabs.datadoghq.com/articles/unpatchable-kubernetes-vulnerabilities-cve-2021-25740/>)

Author: Rory McCune

Published: 2026-05-21T00:00:00Z

Content type: article

Language: en

Sources: [Datadog Security Labs](<https://devfeed.tech/sources/datadog-security-labs.md>)

Topics: [Kubernetes](<https://devfeed.tech/topics/kubernetes.md>), [Vulnerabilities](<https://devfeed.tech/topics/vulnerabilities.md>), [network security](<https://devfeed.tech/topics/network-security.md>), [Deployment](<https://devfeed.tech/topics/deployment.md>), [nginx](<https://devfeed.tech/topics/nginx.md>)

Tags: [kubernetes](<https://devfeed.tech/tags/kubernetes.md>), [network](<https://devfeed.tech/tags/network.md>), [network-security](<https://devfeed.tech/tags/network-security.md>), [server](<https://devfeed.tech/tags/server.md>), [vulnerabilities](<https://devfeed.tech/tags/vulnerabilities.md>), [vulnerability](<https://devfeed.tech/tags/vulnerability.md>)

## AI overview

This article examines CVE-2021-25740, an unpatchable Kubernetes vulnerability in which users able to modify relevant service endpoint objects can redirect shared ingress or load balancer traffic to endpoints in other tenants' namespaces. It explains the Kubernetes service and endpoint mechanisms behind the issue and its risk in multi-tenant clusters.

## Source excerpt

A look at how Kubernetes CVE-2021-25740 allows users with EndpointSlice access to redirect traffic via shared ingress and load balancer services.