VulnerabilityDeferred

CVE-2026-63469

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.

CRITICAL 9.3EPSS —

Does this matter?

High impact if exploited, but EPSS currently rates exploitation as unscored. Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit.

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 4.0: 9.3 CRITICALCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/M
EPSS: No score yet
Public exploits: None in Exploit-DB
CISA KEV: Not listed
Weakness: CWE-94, CWE-116
Source: security-advisories@github.com

References

Source: NVD record, EPSS from FIRST.org, KEV from CISA, exploits from Exploit-DB. Refreshed daily. Download this record as JSON.