CVE-2026-42461

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.

• 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

The application does not perform an authorization check before performing a sensitive operation. Typical impact: unauthorized access to restricted functionality or data.

Kodem intelligence

1. What is CVE-2026-42461? CVE-2026-42461 is a high-severity missing authorization vulnerability in github.com/getarcaneapp/arcane/backend (go), affecting versions < 1.18.0. It is fixed in 1.18.0. The application does not perform an authorization check before performing a sensitive operation.
2. Which versions of github.com/getarcaneapp/arcane/backend are affected by CVE-2026-42461? github.com/getarcaneapp/arcane/backend (go) versions < 1.18.0 is affected.
3. Is there a fix for CVE-2026-42461? Yes. CVE-2026-42461 is fixed in 1.18.0. Upgrade to this version or later.
4. Is CVE-2026-42461 exploitable, and should I be worried? Whether CVE-2026-42461 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
5. What actually determines whether CVE-2026-42461 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
6. How do I fix CVE-2026-42461? Upgrade github.com/getarcaneapp/arcane/backend to 1.18.0 or later.