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CVE-2026-63470

9.3 criticalEPSS 0.5%

Critical (9.3). EPSS 0.5% estimated probability of exploitation activity in the next 30 days.

On this page
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.

Severity

CVSS 4.0

9.3 critical
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
EPSS
0.5% estimated probability of exploitation activity in the next 30 days; 41st percentile. Scored 2026-11-04. A forecast for this CVE across the internet, not for your own systems.
CISA's assessment (SSVC)
Exploitation: PoC · Automatable: yes · Technical impact: total, assessed 2026-11-03. From CISA's Vulnrichment in the CVE List: whether it is exploited, whether exploiting it can be automated, and how much control it gives.
CWEs
CWE-94 Improper Control of Generation of Code (Code Injection)
CWE-116 Improper Encoding or Escaping of Output
OWASP Top 10
A05:2025 Injection
Published
Modified
Record from
the NVD, synced

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Versions

From the CNA's record in the CVE List.

ProductAffected
koxudaxi fastapi-code-generator< 0.8.1

Attack patterns (CAPEC)

  • CAPEC-35 Leverage Executable Code in Non-Executable Files Likelihood: High · Severity: Very High
  • CAPEC-77 Manipulating User-Controlled Variables Likelihood: High · Severity: Very High
  • CAPEC-242 Code Injection Likelihood: High · Severity: High
  • CAPEC-73 User-Controlled Filename Likelihood: High · Severity: High
  • CAPEC-81 Web Server Logs Tampering Likelihood: Medium · Severity: High
  • CAPEC-85 AJAX Footprinting Likelihood: High · Severity: Low
  • CAPEC-104 Cross Zone Scripting Likelihood: Medium · Severity: High

The attack patterns MITRE's CAPEC relates to this record's weaknesses, as MITRE names them. Credits.

References

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