Vulnerability details

CVE-2026-63469

koxudaxi fastapi-code-generator

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

CVSS 4.0
9.3Critical

Official description

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.

CVSS scores

ScoreVersionSourceVector
9.3Critical 4.0 CVEProject cvelistV5 (CNA) (GitHub_M) 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

Affected products

VendorProductVersionsSource
koxudaxi fastapi-code-generator < 0.8.1 CVEProject cvelistV5 (CNA)

References and advisories

4
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Details

Published
2026-11-03
Last updated
2026-11-09
State
Published
Assigner (CNA)
GitHub_M
Kolun priority
20 · Low

Exploit prediction (EPSS)

0.31%
Probability of exploitation in 30 days
24.2%
Percentile (among all CVEs)

SSVC assessment (CISA)

Automatable
Yes
Exploitation
Proof of concept
Technical impact
Total

Weaknesses (CWE)

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