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CURL-CVE-2023-23915

Published Feb 15, 2023·Last modified Apr 25, 2026
Affected Components(0)

No affected components available

Description

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 hostname 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
Risk Scores
Base Score
0.0

Measures severity based on intrinsic characteristics of the vulnerability, independent of environment.

Threat Intelligence
0.0

No exploitation activity has been observed at this time. Continue routine monitoring.

EPSS
0.86%

The exploit probability is very low. The vulnerability is unlikely to be exploited in the next 30 days.

Exploit
Not available

We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.

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