CVE-2026-45626: Arcane Backend OS Command Injection Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-9mvm-4gwg-v8mp",
  "modified" : "2026-06-09T10:30:26Z",
  "published" : "2026-05-18T13:59:22Z",
  "aliases" : [ "CVE-2026-45626" ],
  "summary" : "Arcane Backend: OS Command Injection in Volume Browser ListDirectory via path query parameter",
  "details" : "## Summary\n\n`GET /environments/{id}/volumes/{volumeName}/browse` accepts a `path` query parameter that is passed to a shell command (`sh -c \"find … | while …\"`) inside an Arcane helper container. The path sanitiser blocks `../` traversal but does not strip Bourne-shell metacharacters such as `$()` or backticks, and `strconv.Quote` only escapes Go string metacharacters, not shell substitution sequences. Any authenticated user with access to a browseable volume can execute arbitrary commands inside the helper container; command output is reflected back in the 500 error body.\n\n## Details\n\nThe execution flow is:\n\n1. `BrowseDirectoryInput.Path` (query: `path`) — `backend/internal/huma/handlers/volumes.go:148`\n2. `VolumeHandler.BrowseDirectory` calls `volumeService.ListDirectory(ctx, volumeName, input.Path)` — `backend/internal/huma/handlers/volumes.go:858-865`. Note the route registration at line 412–419 only declares `BearerAuth`/`ApiKeyAuth`; there is no `checkAdmin(ctx)` call (compare with `customize.go`, `system.go`, `swarm.go`, etc., which do enforce admin).\n3. `VolumeService.ListDirectory` runs the user-supplied path through `sanitizeBrowsePathInternal`, then joins it under `/volume`, quotes it with `strconv.Quote`, and embeds it into a `sh -c` command:\n\n```go\n// backend/internal/services/volume_service.go:286-300\nsanitizedPath, err := s.sanitizeBrowsePathInternal(dirPath)\n...\ntargetPath := path.Join(\"/volume\", sanitizedPath)\nquotedPath := strconv.Quote(targetPath)\ncmd := []string{\"sh\", \"-c\", fmt.Sprintf(\n    \"find %s -mindepth 1 -maxdepth 1 | while IFS= read -r f; do out=$(stat -c \\\"%%s %%Y %%f %%A\\\" -- \\\"$f\\\" 2>/dev/null) || continue; printf \\\"%%s\\\\0%%s\\\\0\\\" \\\"$f\\\" \\\"$out\\\"; done\",\n    quotedPath)}\nstdout, _, err := s.execInContainerInternal(ctx, containerID, cmd)\n```\n\nThe sanitiser is insufficient (`backend/internal/services/volume_service.go:1448-1467`):\n\n```go\nfunc (s *VolumeService) sanitizeBrowsePathInternal(input string) (string, error) {\n    trimmed := strings.TrimSpace(input)\n    if trimmed == \"\" || trimmed == \"/\" { return \"/\", nil }\n    cleaned := path.Clean(trimmed)\n    if !path.IsAbs(cleaned) { cleaned = \"/\" + cleaned }\n    if strings.Contains(cleaned, \"/../\") || strings.HasSuffix(cleaned, \"/..\") || cleaned == \"/..\" {\n        return \"\", fmt.Errorf(\"invalid path: path traversal not allowed\")\n    }\n    if !strings.HasPrefix(cleaned, \"/\") { return \"\", fmt.Errorf(\"invalid path: must be absolute\") }\n    return cleaned, nil\n}\n```\n\nOnly `../` patterns are filtered. `$(...)`, backticks, `;`, `&`, `|`, `>`, etc. all pass through unchanged. `strconv.Quote` then wraps the path in Go-style double quotes, which `sh -c` interprets as a regular double-quoted string — and bash performs `$(...)` command substitution inside double quotes.\n\nFor the input `/$( id)`:\n- `sanitizeBrowsePathInternal` returns `/$( id)` (no `../` present).\n- `path.Join(\"/volume\", \"/$( id)\")` → `/volume/$( id)`.\n- `strconv.Quote(...)` → `\"/volume/$( id)\"`.\n- The shell runs `find \"/volume/$( id)\" …`, which expands to `find \"/volume/uid=0(root) gid=0(root) groups=0(root)\" …`. `find` fails because that path does not exist; the stderr containing the substituted command output is propagated by `execInContainerInternal` (volume_service.go:910-918) into a `command exited with code N: …` error, then re-wrapped by `ListDirectory` and returned to the client as a 500 response body.\n\nErrors from the handler at `volumes.go:863-864` are returned via `huma.Error500InternalServerError(err.Error())`, so the substituted output is reflected in plaintext.\n\n**Blast radius / mitigations actually present:**\n- The helper container is created by `createTempContainerInternal` with `NetworkDisabled: true`, no privileged mode, no Docker socket mount, only the target Docker volume bind-mounted (`:ro` for browse). It is auto-removed.\n- Therefore the injection executes inside an isolated, network-disabled container that already has read access to the same files the browse API exposes.\n- However: the injection grants arbitrary command execution within that container (well beyond the find/stat/readlink/head primitives the API exposes), enables data exfiltration via error-message side channel, and lets an attacker probe the helper image / volume in ways the legitimate API forbids (e.g. read symlink targets the API explicitly censors at `volume_service.go:336-356`, read past size limits, etc.).\n- A non-admin authenticated Arcane user is sufficient (no role check on the volumes browser routes), which makes this a privilege/capability extension for users who otherwise cannot run arbitrary `docker exec`.\n\n**Secondary issue (same sanitiser):** `DeleteFile` (`volume_service.go:924-963`) defends against deleting volume root with `if sanitizedPath == \"/\"`. Input `path=.` yields `path.Clean(\".\") == \".\"` → prefixed to `/.`, which fails the `== \"/\"` check, then `path.Join(\"/volume\", \"/.\") == \"/volume\"`, so the executed command is `rm -rf /volume`, recursively deleting all volume contents. This is a separate logic flaw worth fixing alongside the sanitiser hardening but is reported here only for completeness.\n\n## Impact\n\n- Authenticated user (any role, including non-admin) can execute arbitrary shell commands inside the per-volume helper container.\n- Output of those commands is reflected in HTTP 500 error bodies — usable as an exfiltration channel.\n- Attacker gains capabilities the legitimate API withholds: bypass the symlink-target censoring at `volume_service.go:336-356`, bypass per-file byte limits, enumerate the helper image, mount-time inspection, etc.\n- No host compromise: the container has `NetworkDisabled: true`, no privileged flag, no Docker socket; the volume is bind-mounted read-only for browse. Confidentiality/integrity/availability impact is therefore limited (CVSS C:L / I:L / A:L) but real.\n- The same insufficient sanitiser additionally permits a destructive `rm -rf /volume` by sending `path=.` to `DELETE /environments/{id}/volumes/{volumeName}/browse`, which any authenticated user can also reach.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:L"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Go",
      "name" : "github.com/getarcaneapp/arcane/backend"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "last_affected" : "1.18.1"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/getarcaneapp/arcane/security/advisories/GHSA-9mvm-4gwg-v8mp"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-45626"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/getarcaneapp/arcane"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-78" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-05-18T13:59:22Z",
    "nvd_published_at" : "2026-05-29T18:17:10Z"
  }
}