GHSA-68cj-mvg9-rgm2: Capsule: CapsuleConfiguration NodeMetadata regex fields lack webhook validation, allowing MustCompile panic on all Node admission requests

Summary CapsuleConfiguration.Spec.NodeMetadata.ForbiddenLabels.Regex and ForbiddenAnnotations.Regex are never validated by any admission webhook. A Cluster Admin can persist a malformed regex to etcd without being blocked. Once stored, every Node CREATE, UPDATE, or PATCH request triggers regexp.MustCompile() in pkg/api/forbidden_list.go:36, which panics and crashes the node admission webhook — causing a cluster-wide Denial of Service for all Node operations. Root cause internal/webhook/tenant/validation/ contains dedicated regex validators for every Tenant regex field (hostname, storageclass, ingressclass, containerregistry, etc.). internal/webhook/cfg/ contains no regex validator at all — only owners.go, serviceaccount.go, and warnings.go. The downstream consumer internal/webhook/node/user_metadata.go calls: // line 131 matched = forbiddenLabels.RegexMatch(label) // line 150 matched = forbiddenAnnotations.RegexMatch(annotation) Which routes to pkg/api/forbidden_list.go:36: func (in ForbiddenListSpec) RegexMatch(value string) (ok bool) { if len(in.Regex) > 0 { ok = regexp.MustCompile(in.Regex).MatchString(value) // ← panics on invalid regex } return ok } Unlike regexp.Compile, regexp.MustCompile panics instead of returning an error. Since no webhook validates the CapsuleConfiguration regex fields before storage, a malformed value reaches MustCompile on every Node admission request. Comparison with existing CVEs GHSA-f94q-w3w8-cj67 and GHSA-gxjc-74v5-3vx3 affect individual Tenant fields — their validators existed but checked the wrong field. This issue is different: no validator exists at all for CapsuleConfiguration regex fields, and the blast radius is cluster-wide (all Nodes), not scoped to one tenant. PoC package main import ( "fmt" "regexp" ) type ForbiddenListSpec struct{ Regex string } // Exact copy of pkg/api/forbidden_list.go:34-38 func (in ForbiddenListSpec) RegexMatch(value string) bool { if len(in.Regex) > 0 { return regexp.MustCompile(in.R