cert-manager CVE-2026-62290 (GHSA-8rvj-mm4h-c258): namespace users can create ACME Challenge resources directly and make cert-manager use ClusterIssuer DNS01 credentials (credential disclosure with acme-dns). Which versions fix it?

Applies to: cert-manager 1.18.0-1.19.5 and 1.20.0-1.20.2 in clusters where non-admin users can create ACME Challenge resources and ClusterIssuers use DNS01

How it was checked: Compiled on 2026-10-29 from cert-manager's GitHub security advisory, NVD and the fix pull request; not reproduced by Exuvia.

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Fix

What it is: In cert-manager, ACME Challenge resources (challenges.acme.cert-manager.io) are normally created by cert-manager itself from an Order. Before the fix, a user who could create Challenge objects directly in their namespace could point one at a ClusterIssuer and supply their own DNS01 solver settings. cert-manager would then use the ClusterIssuer's DNS provider credentials with attacker-chosen settings and DNS names, bypassing the issuer's solver selectors (dnsZones, dnsNames, matchLabels). With the acme-dns solver, the credentials themselves are sent to a host the attacker controls. Published October 29, 2026 (high). Am I affected: - cert-manager 1.18.0 up to 1.19.5, or 1.20.0 up to 1.20.2 (kubectl get deploy -n cert-manager cert-manager -o jsonpath='{.spec.template.spec.containers[0].image}'). - Real risk in multi-tenant clusters where tenants (or their CI/service accounts) can create challenges.acme.cert-manager.io resources, typically through broad RBAC (wildcard verbs/resources on the acme.cert-manager.io API group, or aggregated edit/admin roles that include it), and where a ClusterIssuer uses DNS01. - Check: kubectl auth can-i create challenges.acme.cert-manager.io --as=system:serviceaccount:<ns>:<sa> -n <ns>. Fix: 1. Upgrade cert-manager to 1.19.6 or 1.20.3 (or later); update the Helm chart and CRDs together as cert-manager documents. 2. Tighten RBAC: ordinary users and workloads should not have create on challenges or orders in acme.cert-manager.io; only cert-manager needs it. Review ClusterRoles that grant it. 3. If tenants could create Challenges, rotate the DNS provider credentials used by ClusterIssuers (acme-dns X-Api-User/Key, cloud DNS keys) and review DNS change logs for records you didn't expect. Verify: the controller image shows v1.19.6+ or v1.20.3+, and kubectl auth can-i shows tenant accounts can no longer create Challenge resources. Sources: https://github.com/cert-manager/cert-manager/security/advisories/GHSA-8rvj-mm4h-c258 https://nvd.nist.gov/vuln/detail/CVE-2026-62290 https://github.com/cert-manager/cert-manager/pull/8940

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