Vulnerability · Published Mar 19, 2026 · Assigned by GitHub_M
CVE-2026-27953ormar has a Pydantic Validation Bypass via Kwargs Injection in Model Constructor
High 7.1
In plain English
A high-severity improper input validation in ormar from ormar-orm. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 1.2% (higher than 69% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official description
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's 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.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian:12 | ormar | no fix listed | DEBIAN-CVE-2026-27953 |
| Debian:14 | ormar | 0.23.1-1 | DEBIAN-CVE-2026-27953 |
| PyPI | ormar | 0.23.1 | GHSA-f964-whrq-44h8 |
| PyPI | ormar | 0.23.1 | PYSEC-2026-2247 |
| Ubuntu:24.04:LTS | ormar | no fix listed | UBUNTU-CVE-2026-27953 |
| Ubuntu:25.10 | ormar | no fix listed | UBUNTU-CVE-2026-27953 |
| Ubuntu:26.04:LTS | ormar | no fix listed | UBUNTU-CVE-2026-27953 |
| Ubuntu:26.10 | ormar | no fix listed | UBUNTU-CVE-2026-27953 |
Affected products (as reported)
Weakness: CWE-915, CWE-20 · Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:L
References
- https://github.com/ormar-orm/ormar/security/advisories/GHSA-f964-whrq-44h8 x_refsource_CONFIRM
- https://github.com/ormar-orm/ormar/commit/7f22aa21a7614b993970345b392dabb0ccde0ab3 x_refsource_MISC
- https://github.com/ormar-orm/ormar/blob/master/examples/fastapi_quick_start.py#L55 x_refsource_MISC
- https://github.com/ormar-orm/ormar/blob/master/ormar/fields/foreign_key.py#L41 x_refsource_MISC
- https://github.com/ormar-orm/ormar/blob/master/ormar/models/helpers/pydantic.py#L108 x_refsource_MISC
- https://github.com/ormar-orm/ormar/blob/master/ormar/models/model.py#L89 x_refsource_MISC
- https://github.com/ormar-orm/ormar/blob/master/ormar/models/newbasemodel.py#L128 x_refsource_MISC
- https://github.com/ormar-orm/ormar/blob/master/ormar/models/newbasemodel.py#L292 x_refsource_MISC
- https://github.com/ormar-orm/ormar/releases/tag/0.23.1 x_refsource_MISC