A sequence injection vulnerability exists in Rack <2.0.9.1, <2.1.4.1 and <2.2.3.1 which could allow is a possible shell escape in the Lint and CommonLogger components of Rack.

A possible denial of service vulnerability exists in Rack <2.0.9.1, <2.1.4.1 and <2.2.3.1 in the multipart parsing component of Rack.

A directory traversal vulnerability exists in rack < 2.2.0 that allows an attacker perform directory traversal vulnerability in the Rack::Directory app that is bundled with Rack which could result in information disclosure.

A reliance on cookies without validation/integrity check security vulnerability exists in rack < 2.2.3, rack < 2.1.4 that makes it is possible for an attacker to forge a secure or host-only cookie prefix.

There is a possible XSS vulnerability in Rack before 2.0.6 and 1.6.11. Carefully crafted requests can impact the data returned by the `scheme` method on `Rack::Request`. Applications that expect the scheme to be limited to 'http' or 'https' and do not escape the return value could be vulnerable to an XSS attack. Note that applications using the normal escaping mechanisms provided by Rails may not impacted, but applications that bypass the escaping mechanisms, or do not use them may be vulnerable.

There is a possible DoS vulnerability in the multipart parser in Rack before 2.0.6. Specially crafted requests can cause the multipart parser to enter a pathological state, causing the parser to use CPU resources disproportionate to the request size.

lib/rack/utils.rb in Rack before 1.5.4 and 1.6.x before 1.6.2, as used with Ruby on Rails 3.x and 4.x and other products, allows remote attackers to cause a denial of service (SystemStackError) via a request with a large parameter depth.

Unspecified vulnerability in Rack::Auth::AbstractRequest in Rack 1.1.x before 1.1.5, 1.2.x before 1.2.7, 1.3.x before 1.3.9, and 1.4.x before 1.4.4 allows remote attackers to cause a denial of service via unknown vectors related to "symbolized arbitrary strings."

multipart/parser.rb in Rack 1.3.x before 1.3.8 and 1.4.x before 1.4.3 allows remote attackers to cause a denial of service (memory consumption and out-of-memory error) via a long string in a Multipart HTTP packet.

lib/rack/multipart.rb in Rack before 1.1.4, 1.2.x before 1.2.6, 1.3.x before 1.3.7, and 1.4.x before 1.4.2 uses an incorrect regular expression, which allows remote attackers to cause a denial of service (infinite loop) via a crafted Content-Disposion header.

Rack::Session::Cookie in Rack 1.5.x before 1.5.2, 1.4.x before 1.4.5, 1.3.x before 1.3.10, 1.2.x before 1.2.8, and 1.1.x before 1.1.6 allows remote attackers to guess the session cookie, gain privileges, and execute arbitrary code via a timing attack involving an HMAC comparison function that does not run in constant time.

rack/file.rb (Rack::File) in Rack 1.5.x before 1.5.2 and 1.4.x before 1.4.5 allows attackers to access arbitrary files outside the intended root directory via a crafted PATH_INFO environment variable, probably a directory traversal vulnerability that is remotely exploitable, aka "symlink path traversals."

Rack before 1.1.3, 1.2.x before 1.2.5, and 1.3.x before 1.3.6 computes hash values for form parameters without restricting the ability to trigger hash collisions predictably, which allows remote attackers to cause a denial of service (CPU consumption) by sending many crafted parameters.