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Date: Wed, 11 May 2022 08:37:37 +0200 (CEST)
From: Daniel Stenberg <>
To: curl security announcements -- curl users <>,, libcurl hacking <>,
Subject: [SECURITY ADVISORY] curl: cookie for trailing dot TLD

cookie for trailing dot TLD

Project curl Security Advisory, May 11 2022 -


libcurl wrongly allows HTTP cookies to be set for Top Level Domains (TLDs) if
the host name is provided with a trailing dot.

curl can be told to receive and send cookies when communicating using
HTTP(S). curl's "cookie engine" can be built with or without [Public Suffix
List]( awareness. If PSL support not provided, a
more rudimentary check exists to at least prevent cookies from being set on
TLDs. This check was broken if the host name in the URL uses a trailing dot.

This can allow arbitrary sites to set cookies that then would get sent to a
different and unrelated site or domain.

We are not aware of any exploit of this flaw.


This vulnerability only exists when curl is built without
[libpsl]( Without this PSL support
built-in, curl is also destined to possibly leak cookies cross sites simply
due to how public suffixes work.

This flaw was introduced in [commit
b27ad8e1d3e68e](, shipped
in curl 7.82.0 when the treatment of trailing dot host names was changed.

This flaw is similar to
[CVE-2014-3620](, although in 2014
curl did not have PSL support.

The Common Vulnerabilities and Exposures (CVE) project has assigned the name
CVE-2022-27779 to this issue.

CWE-201: Information Exposure Through Sent Data

Severity: Medium


- Affected versions: curl 7.82.0 to and including curl 7.83.0
- Not affected versions: curl < 7.82.0 and curl >= 7.83.1

libcurl is used by many applications, but not always advertised as such!


A [fix for CVE-2022-27779](


  A - Upgrade curl to version 7.83.1

  B - Apply the patch to your local version

  C - Build libcurl with libpsl support

  D - Do not use cookies


This issue was reported to the curl project on April 28, 2022. We contacted
distros@...nwall on May 5.

libcurl 7.83.1 was released on May 11 2022, coordinated with the publication
of this advisory.


This issue was reported by Axel Chong. Patched by Daniel Stenberg.

Thanks a lot!


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