PYSEC-2024-38

2024-02-0515:15:00

Google

osv.dev

174

fastapi

web framework

vulnerability

http content-type

python-multipart

regular expression

denial of service

redos

patch

version 0.109.1

CVSS3

7.5

Attack Vector

NETWORK

Attack Complexity

LOW

Privileges Required

NONE

User Interaction

NONE

Scope

UNCHANGED

Confidentiality Impact

NONE

Integrity Impact

NONE

Availability Impact

HIGH

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

AI Score

7.1

Confidence

High

EPSS

0.001

Percentile

47.2%

JSON

FastAPI is a web framework for building APIs with Python 3.8+ based on standard Python type hints. When using form data, python-multipart uses a Regular Expression to parse the HTTP Content-Type header, including options. An attacker could send a custom-made Content-Type option that is very difficult for the RegEx to process, consuming CPU resources and stalling indefinitely (minutes or more) while holding the main event loop. This means that process can’t handle any more requests. It’s a ReDoS(Regular expression Denial of Service), it only applies to those reading form data, using python-multipart. This vulnerability has been patched in version 0.109.1.