Skip to content

Potential Host Header Poisoning on misconfigured servers

daftspunk published GHSA-xhfx-hgmf-v6vp Mar 10, 2021


composer october/backend (composer)

Affected versions


Patched versions




When running on servers that are configured to accept a wildcard as a hostname (i.e. the server routes any request, regardless of the HOST header to an October CMS instance) the potential exists for Host Header Poisoning attacks to succeed. See the following resources for more information on Host Header Poisoning:


A feature has been added in v1.1.2 to allow a set of trusted hosts to be specified in the application.


  • Apply octobercms/library@f86fcbc & f638d3f to your installation manually if unable to upgrade to v1.1.2.

  • Check that the configuration setting cms.linkPolicy is set to force.

Alternative Workaround

Check to make sure that your web server does not accept any hostname when serving your web application.

  1. Add an entry called testing.tld to your computer's host file and direct it to your server's IP address
  2. Open the address testing.tld in your web browser
  3. Make sure an October CMS website is not available at this address

If an October CMS website is returned, configure your webserver to only allow known hostnames. If you require assistance with this, please contact your server administrator.


Reported by Abdullah Hussam

For More Information

If you have any questions or comments about this advisory:

Threat Assessment

Screen Shot 2021-01-15 at 4 12 57 PM