Follow @Openwall on Twitter for new release announcements and other news
[<prev] [next>] [day] [month] [year] [list]
Date: Wed, 15 Feb 2023 08:28:55 +0100 (CET)
From: Daniel Stenberg <>
To: curl security announcements -- curl users <>,, libcurl hacking <>,
Subject: curl: CVE-2023-23915: HSTS amnesia with --parallel

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

Project curl Security Advisory, February 15 2023 -


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

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`
2. `curl --hsts hsts.txt`

We are not aware of any exploit of this flaw.


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

This flaw was introduced in [commit
7385610d0c7](, which was
shipped enabled by default from [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: 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!


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](


  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://`


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

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


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

Thanks a lot!


  | Commercial curl support up to 24x7 is available!
  | Private help, bug fixes, support, ports, new features

Powered by blists - more mailing lists

Please check out the Open Source Software Security Wiki, which is counterpart to this mailing list.

Confused about mailing lists and their use? Read about mailing lists on Wikipedia and check out these guidelines on proper formatting of your messages.