This flaw allows a malicious HTTP server to set "super cookies" in curl that
are then passed back to more origins than what is otherwise allowed or
possible. This allows a site to set cookies that then would get sent to
different and unrelated sites and domains.

It could do this by exploiting a mixed case flaw in curl's function that
verifies a given cookie domain against the Public Suffix List (PSL). For
example a cookie could be set with domain=co.UK when the URL used a lower
case hostname curl.co.uk, even though co.uk is listed as a PSL domain.

References

• https://nvd.nist.gov/vuln/detail/CVE-2023-46218
• https://hackerone.com/reports/2212193
• https://curl.se/docs/CVE-2023-46218.html
• https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/3ZX3VW67N4ACRAPMV2QS2LVYGD7H2MVE/
• https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/UOGXU25FMMT2X6UUITQ7EZZYMJ42YWWD/
• https://lists.debian.org/debian-lts-announce/2023/12/msg00015.html
• https://www.debian.org/security/2023/dsa-5587
• https://security.netapp.com/advisory/ntap-20240125-0007/