CVE-2026-62290: cert-manager: Direct ACME Challenge resources can bypass Issuer DNS01 solver policy and use ClusterIssuer DNS credentials

Challenge resources under acme.cert-manager.io can be created directly by namespace users. On create, cert-manager performs no admission validation tying the Challenge to an Order, an owner reference, or an Issuer-selected solver. The ACME Challenge controller then reconciles the direct resource and uses Challenge.spec.solver as the DNS01 provider configuration.

When the direct Challenge references a ClusterIssuer, cert-manager derives the DNS provider secret namespace and ambient-credential policy from the ClusterIssuer reference, but the DNS provider configuration itself is attacker-controlled through Challenge.spec.solver. This lets a namespace user bypass Issuer/ClusterIssuer solver selectors such as dnsZones, dnsNames, and matchLabels, and make the cert-manager controller use ClusterIssuer DNS credentials for attacker-selected provider settings and DNS names.

In the acme-dns case, this becomes credential disclosure because the attacker-controlled solver host receives the X-Api-User and X-Api-Key headers loaded by cert-manager from the ClusterIssuer resource namespace.