Arcane Docker Manager CVE-2026-42461

Summary

Four GET endpoints under /api/templates* in Arcane's Huma backend are registered without any Security requirement, allowing any unauthenticated network client to list and read the full Compose YAML and .env content of every custom template stored in the instance. Because Arcane's UI exposes a "Save as Template" flow on the project / swarm-stack creation pages that persists the operator's *real* env content (database passwords, API keys, etc.) verbatim, this missing authorization is an unauthenticated read of operator secrets in practice - not a theoretical info-disclosure.

The frontend explicitly treats /customize/templates/* as an authenticated area (PROTECTED_PREFIXES in frontend/src/lib/utils/redirect.util.ts), and every CRUD operation (POST/PUT/DELETE) on the same paths requires a Bearer/API key, so this is a clear backend authorization gap, not intended public access.

Details

Affected file: backend/internal/huma/handlers/templates.go:194-228.

In RegisterTemplates, four huma.Register calls have no Security: block:

// templates.go
huma.Register(api, huma.Operation{
    OperationID: "listTemplatesPaginated",
    Method:      "GET",
    Path:        "/templates",
    ...
    // <-- no Security
}, h.ListTemplates)

huma.Register(api, huma.Operation{
    OperationID: "getAllTemplates",
    Method:      "GET",
    Path:        "/templates/all",
    ...
}, h.GetAllTemplates)

huma.Register(api, huma.Operation{
    OperationID: "getTemplate",
    Method:      "GET",
    Path:        "/templates/{id}",
    ...
}, h.GetTemplate)

huma.Register(api, huma.Operation{
    OperationID: "getTemplateContent",
    Method:      "GET",
    Path:        "/templates/{id}/content",
    ...
}, h.GetTemplateContent)

Arcane's auth bridge (backend/internal/huma/middleware/auth.go:168-172) only enforces authentication when the operation declares one of the security schemes (BearerAuth or ApiKeyAuth). With Security omitted, parseSecurityRequirements returns isRequired=false and the request flows through with no token check.

TemplateHandler.GetTemplateContent (templates.go:478-499) calls templateService.GetTemplateContentWithParsedData (backend/internal/services/template_service.go:1303-1347), which returns the model's Content, EnvContent, parsed services, and parsed env-variable key/value pairs verbatim. The model models.ComposeTemplate (backend/internal/models/template.go:15-16) stores Content and EnvContent as plain text columns and has no owner / user binding.

Impact

• Pre-auth confidentiality breach. An unauthenticated client on the same network (or through any path-unaware reverse proxy) recovers the full envContent of every locally-stored Compose template. Because the supported "Save as Template" workflow takes the operator's real env values verbatim, this commonly includes database passwords, registry tokens, third-party API keys (Stripe, Sentry, etc.), and OIDC client secrets.
• Internal asset enumeration. GET /api/templates returns names, descriptions, tags, and registry metadata for every template, leaking what services the team runs internally and which compose files they reuse