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CVE-2026-63469VulnerabilityPublished

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

Affects fastapi-code-generatorSource GCVE Database

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Authoritative record:CVE-2026-63469· Critical 9.3

Not known to be exploited · CVSS 9.3 Critical : upgrade to 0.8.1 as a priority.

Data as of 9 Nov 2026, 20:20 UTC

CVSS 4.0 base score
9.3Critical
How severe the flaw is on the 0–10 CVSS scale.

Thin evidence

One scorer or none
CVSS scores by source
CNA (GitHub_M)CVSS 4.09.3
Patch
Available – fixed in 0.8.1
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

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 3 Nov 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 9 Nov 2026.

What to do

Upgrade fastapi-code-generator to 0.8.1.

Affected software

ProductAffectedFixed in
PyPIfastapi-code-generatorAffected
  • <0.8.1
Fixed in
  • 0.8.1

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

A patch is available in fastapi-code-generator version 0.8.1 that properly escapes response status-code keys before emitting them into the FastAPI route decorator. Users should upgrade to version 0.8.1 or later. The fix ensures that status-code keys are safely represented as Python string literals and validates that keys conform to expected numeric patterns, preventing injection of arbitrary code. Until upgrading, avoid generating FastAPI code from untrusted or attacker-controlled OpenAPI specifications with multiple responses.

Description

fastapi-code-generator versions prior to 0.8.1 contain a critical import-time remote code execution vulnerability. This occurs because the tool emits response status-code keys into the FastAPI route decorator's responses dictionary as unescaped single-quoted string literals. An attacker-controlled status-code key containing a single quote can break out of the string context and inject arbitrary Python expressions that execute during module import, before any request is made. This affects applications generating FastAPI code from attacker-influenced OpenAPI specs with multiple responses. The vulnerability is fixed in version 0.8.1 by properly escaping status-code keys and validating their format.

References

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