Vulnerability · Published Nov 3, 2026 · Assigned by GitHub_M
CVE-2026-63470fastapi-code-generator: Call-time RCE via operation summary -> unescaped route-handler docstring
Critical 9.3
In plain English
A critical-severity code injection in fastapi-code-generator from koxudaxi. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.5% (higher than 41% of all known vulnerabilities).
Official description
fastapi-code-generator creates FastAPI applications from OpenAPI files. Prior to 0.8.1, the generator inserts Operation.summary into a generated route-handler docstring as a triple-double-quoted string without escaping embedded triple quotes. An attacker-controlled or attacker-influenced operation summary can close the docstring and inject a valid Python expression statement into the handler body. Syntax-breaking input only causes generation to fail, but syntactically valid generated code executes with the server process's privileges when the affected route handler is called. This call-time route-handler docstring sink is distinct from the project's separate import-time route-path and additional-response-key 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-h667-4jj2-cgv4 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