urllib3 doesn't treat the Cookie
HTTP header special or provide any helpers for managing cookies over HTTP, that is the responsibility of the user. However, it is possible for a user to specify a Cookie
header and unknowingly leak information via HTTP redirects to a different origin if that user doesn't disable redirects explicitly.
Users must handle redirects themselves instead of relying on urllib3's automatic redirects to achieve safe processing of the Cookie
header, thus we decided to strip the header by default in order to further protect users who aren't using the correct approach.
We believe the number of usages affected by this advisory is low. It requires all of the following to be true to be exploited:
Cookie
header on requests, which is mostly typical for impersonating a browser.redirects=False
when sending requests.Cookie
header.