curl: CVE-2023-23915: HSTS amnesia with --parallel

[Daniel Stenberg <daniel () haxx se>]

CVE-2023-23915: HSTS amnesia with --parallel
============================================

Project curl Security Advisory, February 15 2023 -
[Permalink](https://curl.se/docs/CVE-2023-23915.html)

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

curl's HSTS cache saving behaves wrongly when multiple URLs are requested in
parallel.

Using its HSTS support, curl can be instructed to use HTTPS instead of using
an insecure clear-text HTTP step even when HTTP is provided in the URL. This
HSTS mechanism would however surprisingly fail when multiple transfers are done
in parallel as the HSTS cache file gets overwritten by the most recently
completed transfer.

A later HTTP-only transfer to the earlier host name would then *not* get
upgraded properly to HSTS.

Reproducible like this:

1. `curl --hsts hsts.txt --parallel https://curl.se https://example.com`
2. `curl --hsts hsts.txt http://curl.se`

We are not aware of any exploit of this flaw.

INFO
----

This is a curl command line issue and does not affect libcurl.

This flaw was introduced in [commit
7385610d0c7](https://github.com/curl/curl/commit/7385610d0c7), which was
shipped enabled by default from [commit
d71ff2b9db566b3f](https://github.com/curl/curl/commit/d71ff2b9db566b3f) in
curl 7.77.0.

The Common Vulnerabilities and Exposures (CVE) project has assigned the name
CVE-2023-23915 to this issue.

CWE-319: Cleartext Transmission of Sensitive Information

Severity: Low

AFFECTED VERSIONS
-----------------

- Affected versions: curl 7.77.0 to and including 7.87.0
- Not affected versions: curl < 7.77.0 and curl >= 7.88.0

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

THE SOLUTION
------------

7.88.0 will share the HSTS state properly between transfers, making each
subsequent save store a complete state.

A [fix for CVE-2023-23914](https://github.com/curl/curl/pull/10138)

RECOMMENDATIONS
--------------

 A - Upgrade curl to version 7.88.0

 B - Apply the patch to your local version

 C - Specify all URLs with `HTTPS://` and not `HTTP://`

TIMELINE
--------

This issue was reported to the curl project on December 21, 2022. We contacted
distros@openwall on February 7, 2022.

curl 7.88.0 was released on February 15 2023, coordinated with the publication
of this advisory.

CREDITS
-------

- Reported-by: Harry Sintonen
- Patched-by: Daniel Stenberg

Thanks a lot!

--

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