Internet Bug Bounty · Report #2274981
curl cookie mixed case PSL bypass
Summary
CVE-2023-46218 - cookie mixed case PSL bypass
VULNERABILITY 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 lowercase hostname curl.co.uk, even though co.uk is listed as a PSL domain.
Full Security Advisory: https://curl.se/docs/CVE-2023-46218.html
How it was found
A vulnerability in curl 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 lowercase hostname curl.co.uk, even though co.uk is listed as a PSL domain.
Impact
Issue supercookies bypassing the Public Suffix List check.