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GHSA-2rqw-v265-jf8c

MediumCVSS 6.1 / 10
Published Aug 26, 2021·Last modified Feb 21, 2024
Affected Components(0)

No affected components available

Description

Overview

There is a possible open redirect vulnerability in the Host Authorization middleware in Action Pack. This vulnerability has been assigned the CVE identifier CVE-2021-22942.

Versions Affected: >= 6.0.0. Not affected: < 6.0.0 Fixed Versions: 6.1.4.1, 6.0.4.1

Impact

Specially crafted “X-Forwarded-Host” headers in combination with certain “allowed host” formats can cause the Host Authorization middleware in Action Pack to redirect users to a malicious website.

Impacted applications will have allowed hosts with a leading dot. For example, configuration files that look like this:

config.hosts <<  '.EXAMPLE.com'

When an allowed host contains a leading dot, a specially crafted Host header can be used to redirect to a malicious website.

This vulnerability is similar to CVE-2021-22881, but CVE-2021-22881 did not take in to account domain name case sensitivity.

Releases

The fixed releases are available at the normal locations.

Workarounds

In the case a patch can’t be applied, the following monkey patch can be used in an initializer:

module ActionDispatch
  class HostAuthorization
    HOSTNAME = /[a-z0-9.-]+|\[[a-f0-9]*:[a-f0-9.:]+\]/i
    VALID_ORIGIN_HOST = /\A(#{HOSTNAME})(?::\d+)?\z/
    VALID_FORWARDED_HOST = /(?:\A|,[ ]?)(#{HOSTNAME})(?::\d+)?\z/

    private
      def authorized?(request)
        origin_host =
          request.get_header("HTTP_HOST")&.slice(VALID_ORIGIN_HOST, 1) || ""
        forwarded_host =
          request.x_forwarded_host&.slice(VALID_FORWARDED_HOST, 1) || ""
        @permissions.allows?(origin_host) &&
          (forwarded_host.blank? || @permissions.allows?(forwarded_host))
      end
  end
end
Risk Scores
Base Score
6.1

The vulnerability can be exploited over the network without needing physical access. It is easy for an attacker to exploit this vulnerability. An attacker does not need any special privileges or access rights. The attacker needs the user to perform some action, like clicking a link. The vulnerability can affect other systems as well, not just the initial system. There is a low impact on the confidentiality of the information. There is a low impact on the integrity of the data.

Threat Intelligence
5.6

Exploitation attempts have been detected. Elevated vigilance and prompt remediation are advised.

EPSS
1.64%

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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Medium severity
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