There is a possible Open Redirect Vulnerability in Action Pack. This
vulnerability has been assigned the CVE identifier CVE-2021-22903.
Versions Affected: >= v6.1.0.rc2
Not affected: < v6.1.0.rc2
Fixed Versions: 184.108.40.206
This is similar to CVE-2021-22881: Specially crafted Host headers in
combination with certain "allowed host" formats can cause the Host
Authorization middleware in Action Pack to redirect users to a malicious
Since rails/rails@9bc7ea5, strings in config.hosts that do not have a leading
dot are converted to regular expressions without proper escaping. This causes,
for example, config.hosts << "sub.example.com
" to permit a request with a Host
The fixed releases are available at the normal locations.
The following monkey patch put in an initializer can be used as a workaround:
To aid users who aren't able to upgrade immediately we have provided patches for
the two supported release series. They are in git-am format and consist of a
* 6-1-open-redirect.patch - Patch for 6.1 series
Please note that only the 6.1.Z, 6.0.Z, and 5.2.Z series are supported at
present. Users of earlier unsupported releases are advised to upgrade as soon
as possible as we cannot guarantee the continued availability of security
fixes for unsupported releases.