---
id: "CVE-2026-63469"
kind: "vulnerability"
aliases: ["CVE-2026-63469"]
title: "fastapi-code-generator: crafted OpenAPI response key injects Python code"
severity: "critical"
cvss: 9.3
epss: null
exploited: false
status: "open"
category: "package"
products: []
ecosystems: []
tags: ["ci", "fastapi", "openapi", "package", "python"]
not_affected_if: ["trusted-openapi-only", "version-0.8.1-or-later"]
published_at: "2026-11-03T20:18:15+00:00"
first_seen_at: "2026-11-03T20:49:22+00:00"
updated_at: "2026-11-03T20:49:43+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-63469", "first_seen_at": "2026-11-03T20:49:22+00:00"}]
---

# fastapi-code-generator: crafted OpenAPI response key injects Python code

fastapi-code-generator turns OpenAPI files into FastAPI applications and, before 0.8.1, wrote a non-primary response status-code key into generated Python without escaping quotes. An attacker who controls that OpenAPI input can make the generated code run arbitrary Python with the privileges of the app or CI process that imports it.

_Summary, check and fix written by a model from the sources; labelled as such._

## How to check

- Check the installed version of fastapi-code-generator, for example with `pip show fastapi-code-generator`, and see whether it is below `0.8.1`.
- Look for CI jobs or pipelines that run fastapi-code-generator on OpenAPI files from outside the team.
- Review generated FastAPI modules for responses={...} dictionaries with unusual keys.

## Fix

- fastapi-code-generator: move to `0.8.1`

## Timeline

- 2026-11-03T20:49:22+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-63469

## Documents

- [advisory] Vendor advisory: github.com https://github.com/koxudaxi/fastapi-code-generator/security/advisories/GHSA-6xmv-cjr5-w3q8
- [fix] Patch: github.com https://github.com/koxudaxi/fastapi-code-generator/commit/49301dbdb82170d7f50877419d994b05cb1fa2bc
- [fix] Patch: github.com https://github.com/koxudaxi/fastapi-code-generator/commit/b3b9bd66e0b0c4d8c686fda700258104615a1332
- [fix] Release notes: github.com https://github.com/koxudaxi/fastapi-code-generator/releases/tag/0.8.1

## From the sources

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.

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_Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai_