Does Flask-CORS fully support IPv6 origins?

[omar-ashraf1488]

Hi there,

I encountered a situation with IPv6 localhost addresses and wanted to clarify whether Flask-CORS officially supports them.

Setup:

Flask backend running on port 5001.

Flask-CORS configuration:

from flask import Flask
from flask_cors import CORS

app = Flask(__name__)
CORS(app, origins=["http://[::1]:8000"])  # IPv6 localhost

@app.route("/origin")
def origin():
    return "Hello"

Frontend accessed via: http://[::1]:8000/client.html

Problem:

The browser sends Origin: http://[::1]:8000

Flask-CORS does not seem to add the Access-Control-Allow-Origin header, and the browser blocks the request.

Switching to IPv4 (http://127.0.0.1:8000) works as expected.

Question:

• Is this a known limitation?
• Does Flask-CORS currently fully support IPv6 origins?

Thanks for any clarification or guidance!

[valerianb]

The presence of [ and ] (

flask-cors/flask_cors/core.py

Line 266 in fa55dcb

def probably_regex(maybe_regex):

) make your origin being used as a regex.
You could circumvent this by passing directly a valid regex for your use case.