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[SECURITY ADVISORY] curl: cookie for trailing dot TLD

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From: Daniel Stenberg via curl-users <curl-users_at_lists.haxx.se>
Date: Wed, 11 May 2022 08:37:37 +0200 (CEST)

cookie for trailing dot TLD
===========================

Project curl Security Advisory, May 11 2022 -
[Permalink](https://curl.se/docs/CVE-2022-27779.html)

VULNERABILITY
-------------

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](https://publicsuffix.org/) 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.

INFO

----
This vulnerability only exists when curl is built without
[libpsl](https://rockdaboot.github.io/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](https://github.com/curl/curl/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](https://curl.se/docs/CVE-2014-3620.html), 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
-----------------
- 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!
THE SOLUTION
------------
A [fix for CVE-2022-27779](https://github.com/curl/curl/commit/7e92d12b4e6911f)
RECOMMENDATIONS
--------------
  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
TIMELINE
--------
This issue was reported to the curl project on April 28, 2022. We contacted
distros_at_openwall on May 5.
libcurl 7.83.1 was released on May 11 2022, coordinated with the publication
of this advisory.
CREDITS
-------
This issue was reported by Axel Chong. Patched by Daniel Stenberg.
Thanks a lot!
-- 
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Received on 2022-05-11

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