Vulnerability · Published Nov 3, 2026 · Assigned by GitHub_M
CVE-2026-63469fastapi-code-generator: Import-time RCE via response status-code key -> unescaped @app.get(..., responses={...}) dict
Critical 9.3
In plain English
A critical-severity code injection in fastapi-code-generator from koxudaxi. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.3% (higher than 24% of all known vulnerabilities).
Official description
fastapi-code-generator creates FastAPI applications from OpenAPI files. Prior to 0.8.1, the generator inserts an additional response status-code key into the generated responses={...} route-decorator dictionary as a single-quoted Python string without escaping embedded quotes. A multi-response OpenAPI operation with an attacker-controlled or attacker-influenced second non-primary response key can close the dictionary-key literal and inject a valid Python expression. Syntax-breaking input only causes generation to fail, but syntactically valid generated code executes with the application's or CI process's privileges when the generated module is imported and its decorator arguments are evaluated. This additional-response-key sink is distinct from the project's separate route-path and operation-summary sinks. This issue is fixed in version 0.8.1.
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| koxudaxi | fastapi-code-generator | < 0.8.1 |
Weakness: CWE-94, CWE-116 · Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
References
- https://github.com/koxudaxi/fastapi-code-generator/security/advisories/GHSA-6xmv-cjr5-w3q8 x_refsource_CONFIRM
- https://github.com/koxudaxi/fastapi-code-generator/commit/49301dbdb82170d7f50877419d994b05cb1fa2bc x_refsource_MISC
- https://github.com/koxudaxi/fastapi-code-generator/commit/b3b9bd66e0b0c4d8c686fda700258104615a1332 x_refsource_MISC
- https://github.com/koxudaxi/fastapi-code-generator/releases/tag/0.8.1 x_refsource_MISC