kubernetes-sigs/cluster-api

[e2e] Error: "tls: failed to verify certificate: x509: certificate signed by unknown authority"

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#13,300 opened on Feb 3, 2026

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Description

Which jobs are flaking?

periodic-cluster-api-e2e-mink8s-release-1-11 periodic-cluster-api-e2e-latestk8s-main periodic-cluster-api-e2e-release-1-11

Which tests are flaking?

  • capi-e2e [It] When following the Cluster API quick-start with dualstack and ipv4 primary [IPv6] Should create a workload cluster [IPv6]
  • capi-e2e [It] When following the Cluster API quick-start Should create a workload cluster
  • capi-e2e [It] When following the Cluster API quick-start with v1beta1 ClusterClass [ClusterClass] Should create a workload cluster [ClusterClass]
  • When testing Cluster API working on self-hosted clusters using ClusterClass with a HA control plane [ClusterClass] Should pivot the bootstrap cluster to a self-hosted cluster [ClusterClass]
  • capi-e2e [It] When testing Cluster API working on self-hosted clusters using ClusterClass [ClusterClass] Should pivot the bootstrap cluster to a self-hosted cluster [ClusterClass]

Since when has it been flaking?

Jan 23 2026

Testgrid link

https://storage.googleapis.com/k8s-triage/index.html?text=tls%3A%20failed%20to%20verify%20certificate&job=.*cluster-api&xjob=.*-provider-

Reason for failure (if possible)

Failure to call webhook because of tls: failed to verify certificate: x509: certificate signed by unknown authority

Anything else we need to know?

First occurrence is Jan 23 2026 but the error peaked Jan 28 and Feb 3 with multiple errors per day

I noticed cert-manager bump was merged around the time the first peak happened https://github.com/kubernetes-sigs/cluster-api/pull/13279 https://github.com/kubernetes-sigs/cluster-api/pull/13278 https://github.com/kubernetes-sigs/cluster-api/pull/13277

Label(s) to be applied

/kind flake One or more /area label. See https://github.com/kubernetes-sigs/cluster-api/labels?q=area for the list of labels.

Contributor guide

Research direction
Investigate the cert manager bump PRs (#13277, #13278, #13279) for changes that may have affected webhook certificate generation or rotation. Examine the webhook configuration and ensure the certificate chain is properly trusted by the clients. Look at the failing test logs to identify which webhook is failing and trace the certificate verification path.
Tech stack
go
Domain
backendinfrastructure
Issue type
Bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
Half day
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
Active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Mostly clear
Prerequisites
GoKubernetesTLScert manager
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
25