koxudaxi
Fastapi-code-generator: Import-time RCE via response status-code key -> unescaped @app.get(..., responses={...}) dict
Not on CISA's list of exploited flaws, and not in the news we track.
CVE-2026-63469Critical9.3
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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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Chance of exploitation in the next 30 days
0.31%
EPSS score from FIRST
Updated 13 Nov 2026, 12:04 UTC, 31 of 36 sources answering.
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