Denial of Service Vulnerability in Rack Multipart Parsing

There is a possible denial of service vulnerability in the multipart parsing
component of Rack. This vulnerability has been assigned the CVE identifier
CVE-2022-30122.

Versions Affected: >= 1.2
Not affected: < 1.2
Fixed Versions: 2.0.9.1, 2.1.4.1, 2.2.3.1

Impact

Carefully crafted multipart POST requests can cause Rack’s multipart parser to
take much longer than expected, leading to a possible denial of service
vulnerability.

Impacted code will use Rack’s multipart parser to parse multipart posts. This
includes directly using the multipart parser like this:

params = Rack::Multipart.parse_multipart(env)

But it also includes reading POST data from a Rack request object like this:

p request.POST # read POST data
p request.params # reads both query params and POST data

All users running an affected release should either upgrade or use one of the
workarounds immediately.

Workarounds

There are no feasible workarounds for this issue.