Impact
Cookie headers on requests are sensitive information. On making a request using the https scheme to a server which responds with a redirect to a URI with the http scheme, or on making a request to a server which responds with a redirect to a a URI to a different host, we should not forward the Cookie header on. Prior to this fix, only cookies that were managed by our cookie middleware would be safely removed, and any Cookie header manually added to the initial request would not be stripped. We now always strip it, and allow the cookie middleware to re-add any cookies that it deems should be there.
Patches
Affected Guzzle 7 users should upgrade to Guzzle 7.4.4 as soon as possible. Affected users using any earlier series of Guzzle should upgrade to Guzzle 6.5.7 or 7.4.4.
Workarounds
An alternative approach would be to use your own redirect middleware, rather than ours, if you are unable to upgrade. If you do not require or expect redirects to be followed, one should simply disable redirects all together.
References
For more information
If you have any questions or comments about this advisory, please get in touch with us in #guzzle on the PHP HTTP Slack. Do not report additional security advisories in that public channel, however – please follow our vulnerability reporting process.