CVE-2026-63469 PUBLISHED

fastapi-code-generator: Import-time RCE via response status-code key -> unescaped @app.get(..., responses={...}) dict

Assigner: GitHub_M
Reserved: 16.07.2026 Published: 03.11.2026 Updated: 03.11.2026

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.

Metrics

CVSS 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
CVSS Score: 9.3

Product Status

Vendor koxudaxi
Product fastapi-code-generator
Versions
  • Version < 0.8.1 is affected

References

Problem Types

  • CWE-94: Improper Control of Generation of Code ('Code Injection') CWE
  • CWE-116: Improper Encoding or Escaping of Output CWE