There is a possible denial of service vulnerability in the multipart parsing
component of Rack. This vulnerability has been assigned the CVE identifier
Versions Affected: >= 1.2
Not affected: < 1.2
Fixed Versions: 18.104.22.168, 22.214.171.124, 126.96.36.199
Carefully crafted multipart POST requests can cause Rack's multipart parser to
take much longer than expected, leading to a possible denial of service
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
The FIXED releases are available at the normal locations.
There are no feasible workarounds for this issue.
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
* 2-0-multipart-redos.patch - Patch for 2.0 series
* 2-1-multipart-redos.patch - Patch for 2.1 series
* 2-2-multipart-redos.patch - Patch for 2.2 series
Thanks to [@ooooooo_q](https://hackerone.com/ooooooo_q?type=user) for reporting this!