{
  "affected": [
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 1.18.1"
      },
      "package": {
        "ecosystem": "Go",
        "name": "github.com/getarcaneapp/arcane/backend"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "1.19.0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-45627"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-79"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-05-18T14:19:26Z",
    "nvd_published_at": null,
    "severity": "HIGH"
  },
  "details": "## Summary\n\nThe unauthenticated `GET /api/app-images/logo` endpoint reflects a user-supplied `color` query parameter into the body of an SVG document via `strings.ReplaceAll` with no escaping. The substitution lands inside a `\u003cstyle\u003e` element of the embedded `logo.svg`, allowing an attacker to close the style block and inject executable `\u003cscript\u003e` content. Because the response is served as `image/svg+xml` and Arcane sets no Content-Security-Policy or `X-Content-Type-Options` headers, navigating a logged-in admin victim to a crafted URL executes attacker-controlled JavaScript in Arcane\u0027s origin and rides the victim\u0027s HttpOnly JWT cookie to fully compromise the admin account.\n\n## Details\n\nThe route is registered in `backend/internal/huma/handlers/appimages.go:53-61` with an explicitly empty security requirement, marking it as public:\n\n```go\nhuma.Register(api, huma.Operation{\n    OperationID: \"get-logo\",\n    Method:      http.MethodGet,\n    Path:        \"/app-images/logo\",\n    ...\n    Security:    []map[string][]string{}, // explicit: no auth\n}, h.GetLogo)\n```\n\n`backend/internal/huma/middleware/auth.go:209-213` honors the empty `Security` value by returning `reqs.isRequired == false` and short-circuiting with `next(ctx)`, so no JWT/API-key check runs.\n\n`GetLogoInput.Color` (`appimages.go:23`) is declared with no validation tags:\n\n```go\ntype GetLogoInput struct {\n    Full  bool   `query:\"full\" default:\"false\" ...`\n    Color string `query:\"color\" doc:\"Optional accent color override ...\"`\n}\n```\n\nThe handler passes the value straight through `getImageWithColor` \u2192 `ApplicationImagesService.GetImageWithColor` \u2192 `applyAccentColorToSVG` (`backend/internal/services/app_images_service.go:79-105`):\n\n```go\nsvgStr = strings.ReplaceAll(svgStr, \"fill:#6D28D9\", fmt.Sprintf(\"fill:%s\", accentColor))\nsvgStr = strings.ReplaceAll(svgStr, \"fill:#6d28d9\", fmt.Sprintf(\"fill:%s\", accentColor))\n```\n\nThe bundled `backend/resources/images/logo.svg` contains:\n\n```xml\n\u003cstyle id=\"style1\" type=\"text/css\"\u003e.st0{fill:#6d28d9}\u003c/style\u003e\n```\n\nso a `color` value like `red}\u003c/style\u003e\u003cscript\u003efetch(\u0027/api/users\u0027,...)\u003c/script\u003e\u003cstyle\u003ex{` produces a valid SVG that closes the `\u003cstyle\u003e` element and embeds a `\u003cscript\u003e` element. The response Content-Type is `image/svg+xml` (from `pkg/utils/image/image_util.go`), and a grep of the backend confirms no `Content-Security-Policy`, `X-Content-Type-Options`, or framing headers are emitted on any route.\n\nBrowsers execute scripts in SVG documents loaded as top-level navigations or via `\u003ciframe src=\u2026\u003e` / `window.open(\u2026)`. The execution context is `origin(arcane-host)`, so the victim\u0027s `__Host-token` / `token` HttpOnly JWT cookie (recognized by `extractTokenFromCookieHeaderInternal` at `auth.go:274-286`) is automatically attached to subsequent same-origin `fetch()` calls. From there the attacker can invoke any privileged API the victim possesses \u2014 most damagingly `POST /api/users` to create a new admin account, after which the attacker has standalone admin access to manage Docker containers, registries, GitOps secrets, and SSH/registry credentials stored by Arcane.\n\n## Impact\n\n- Same-origin script execution from an unauthenticated, reachable URL \u2014 only user interaction (clicking/visiting the crafted link) is required.\n- Full session-riding against any authenticated user, including admins. Because Arcane manages Docker daemons, container exec, image registries, and GitOps repositories, an attacker who lands script execution as an admin victim can:\n  - Create persistent attacker-controlled admin accounts via `POST /api/users`.\n  - Read/modify secrets stored in environments, registries, and Git repositories the admin can access.\n  - Start or exec into containers on connected Docker hosts.\n- HttpOnly cookies do not mitigate the issue \u2014 cookies are auto-attached to same-origin `fetch()`. Absence of CSP and `X-Content-Type-Options: nosniff` removes available defenses-in-depth.\n\nDefense-in-depth \u2014 add to all responses (and especially to `/api/app-images/*`):\n\n- `X-Content-Type-Options: nosniff`\n- `Content-Security-Policy: default-src \u0027none\u0027; style-src \u0027unsafe-inline\u0027; img-src \u0027self\u0027 data:` on the SVG image responses (or the most permissive policy compatible with the frontend on app routes).\n- Consider serving these images with `Content-Disposition: inline` and from a separate cookie-less origin to remove the same-origin session-riding primitive entirely.\n\nAlso enforce the same allowlist on the settings write path (`SettingsService` \u2192 `AccentColor`) so a stored XSS variant cannot be introduced via the settings API.",
  "id": "GHSA-q2pj-8v84-9mh5",
  "modified": "2026-05-18T14:19:27Z",
  "published": "2026-05-18T14:19:26Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/getarcaneapp/arcane/security/advisories/GHSA-q2pj-8v84-9mh5"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/getarcaneapp/arcane"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:L/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Arcane Backend: Unauthenticated reflected XSS via SVG color parameter enables admin account takeover"
}