.. _urlsplit-nfkc-normalization:

urlsplit does not handle NFKC normalization
===========================================

.. warning::
    This resource is maintained for historical reference and **does not contain the latest vulnerability info for Python**.

    The `canonical database for vulnerabilities affecting Python <https://github.com/psf/advisory-database>`_ is available on GitHub
    in the Open Source Vulnerability (OSV) format. This vulnerability can be viewed online at the
    `Open Source Vulnerability Database <https://osv.dev/list?ecosystem=&q=CVE-2019-9636>`_.

URLs encoded with Punycode/IDNA use NFKC normalization to decompose
characters. This can result in some characters introducing new segments
into a URL.

See `Unicode® Technical Standard #46: Unicode IDNA Compatibility Processing
<https://unicode.org/reports/tr46/>`_.

Dates:

* Disclosure date: **2019-03-06** (Python issue bpo-36216 reported)
* Reported at: 2019-02-16 (email to PSRT)
* Reported by: Jonathan Birch of Microsoft Corporation and Panayiotis Panayiotou

Fixed In
--------

* Python **2.7.17** (2019-10-19) fixed by `commit e37ef41 (branch 2.7) <https://github.com/python/cpython/commit/e37ef41289b77e0f0bb9a6aedb0360664c55bdd5>`_ (2019-03-07)
* Python **3.5.7** (2019-03-18) fixed by `commit c0d9511 (branch 3.5) <https://github.com/python/cpython/commit/c0d95113b070799679bcb9dc49d4960d82e8bb08>`_ (2019-03-11)
* Python **3.6.9** (2019-07-02) fixed by `commit 23fc041 (branch 3.6) <https://github.com/python/cpython/commit/23fc0416454c4ad5b9b23d520fbe6d89be3efc24>`_ (2019-03-12)
* Python **3.7.3** (2019-03-25) fixed by `commit daad2c4 (branch 3.7) <https://github.com/python/cpython/commit/daad2c482c91de32d8305abbccc76a5de8b3a8be>`_ (2019-03-07)
* Python **3.8.0** (2019-10-14) fixed by `commit 16e6f7d (branch 3.8) <https://github.com/python/cpython/commit/16e6f7dee7f02bb81aa6b385b982dcdda5b99286>`_ (2019-03-07)

Python issue
------------

CVE-2019-9636: urlsplit does not handle NFKC normalization.

* Python issue: `bpo-36216 <https://bugs.python.org/issue36216>`_
* Creation date: 2019-03-06
* Reporter: Steve Dower

CVE-2019-9636
-------------

Python 2.7.x through 2.7.16 and 3.x through 3.7.2 is affected by: Improper Handling of Unicode Encoding (with an incorrect netloc) during NFKC normalization. The impact is: Information disclosure (credentials, cookies, etc. that are cached against a given hostname). The components are: urllib.parse.urlsplit, urllib.parse.urlparse. The attack vector is: A specially crafted URL could be incorrectly parsed to locate cookies or authentication data and send that information to a different host than when parsed correctly. This is fixed in: v2.7.17, v2.7.17rc1, v2.7.18, v2.7.18rc1; v3.5.10, v3.5.10rc1, v3.5.7, v3.5.8, v3.5.8rc1, v3.5.8rc2, v3.5.9; v3.6.10, v3.6.10rc1, v3.6.11, v3.6.11rc1, v3.6.12, v3.6.9, v3.6.9rc1; v3.7.3, v3.7.3rc1, v3.7.4, v3.7.4rc1, v3.7.4rc2, v3.7.5, v3.7.5rc1, v3.7.6, v3.7.6rc1, v3.7.7, v3.7.7rc1, v3.7.8, v3.7.8rc1, v3.7.9.

* CVE ID: `CVE-2019-9636 <https://nvd.nist.gov/vuln/detail/CVE-2019-9636/>`_
* Published: 2019-03-08
* `CVSS Score <https://nvd.nist.gov/cvss.cfm>`_: 5.0

Timeline
--------

Timeline using the disclosure date **2019-03-06** as reference:

* 2019-02-16 (**-18 days**): Reported (email to PSRT)
* 2019-03-06: `Python issue bpo-36216 <https://bugs.python.org/issue36216>`_ reported by Steve Dower
* 2019-03-07 (**+1 days**): `commit 16e6f7d (branch 3.8) <https://github.com/python/cpython/commit/16e6f7dee7f02bb81aa6b385b982dcdda5b99286>`_
* 2019-03-07 (**+1 days**): `commit daad2c4 (branch 3.7) <https://github.com/python/cpython/commit/daad2c482c91de32d8305abbccc76a5de8b3a8be>`_
* 2019-03-07 (**+1 days**): `commit e37ef41 (branch 2.7) <https://github.com/python/cpython/commit/e37ef41289b77e0f0bb9a6aedb0360664c55bdd5>`_
* 2019-03-08 (**+2 days**): CVE-2019-9636 published
* 2019-03-11 (**+5 days**): `commit c0d9511 (branch 3.5) <https://github.com/python/cpython/commit/c0d95113b070799679bcb9dc49d4960d82e8bb08>`_
* 2019-03-12 (**+6 days**): `commit 23fc041 (branch 3.6) <https://github.com/python/cpython/commit/23fc0416454c4ad5b9b23d520fbe6d89be3efc24>`_
* 2019-03-18 (**+12 days**): Python 3.5.7 released
* 2019-03-25 (**+19 days**): Python 3.7.3 released
* 2019-07-02 (**+118 days**): Python 3.6.9 released
* 2019-10-14: Python 3.8.0 released
* 2019-10-19 (**+227 days**): Python 2.7.17 released