A flaw in curl’s cookie parsing logic allows a malicious HTTP server to set 'super cookies' that bypass the Public Suffix List check. This enables an attacker-controlled origin to inject cookies that curl subsequently scopes and transmits to unrelated third-party domains.

Last updated 2 July 2026

curl supports "globbing" of URLs, in which a user can pass a numerical range to have the tool iterate over those numbers to do a sequence of transfers.

In the globbing function that parses the numerical range, there was an omission that made curl read a byte beyond the end of the URL if given a carefully crafted, or just wrongly written, URL. The URL is stored in a heap based buffer, so it could then be made to wrongly read something else instead of crashing.

Affected versions: curl 7.34.0 up to and including 7.54.1

This flaw only affects the curl command line tool, not the libcurl library.

cURL libcurl could allow a remote attacker to bypass security restrictions, caused by a mixed case flaw when curl is built without PSL support. By sending a specially crafted request, an attacker could exploit this vulnerability to allow a HTTP server to set "super cookies" in curl.