CVE-2026-63469: fastapi-code-generator: Import-time RCE via response status-code key -> unescaped @app.get(..., responses={...}) dict

Is it exploited?

Not on CISA's list. CISA has not added it to the Known Exploited Vulnerabilities catalog as of 10 Nov 2026. If CISA adds it, this page shows it as known exploited.

How likely is exploitation in the next 30 days?

0.3%

EPSS score, percentile 24.5 of all scored records. A probability estimated by FIRST, not a report of exploitation.

CISA's SSVC assessment in the CVE record lists exploitation as poc.

How severe?

9.3 Critical

CVSS v4.0 base score, given by the CNA

What should I do?

CISA has set no required action, because the vulnerability is not in KEV.

No patch or vendor advisory is listed in the CVE record. Check koxudaxi's advisories.

Which versions are affected?

Affected

• < 0.8.1

Versions by product

Source: CISA KEV 2026.11.10, as of 10 Nov 2026; FIRST EPSS, as of 12 Nov 2026; CVE List, as of 12 Nov 2026. About the data.

Description

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

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.

Source: CVE List, as of 12 Nov 2026. About the data.

What to do

Advisories and patches

No patch, vendor advisory or mitigation is listed in the CVE record. Check koxudaxi's own security advisories for a fix, and compare your version with the affected versions below.

This summary is based on the CVE record as of 12 Nov 2026. Check the vendor's advisory before you act: affected versions and fixes can change.

Affected products and versions

Source: CVE List, as of 12 Nov 2026. About the data.

Timeline