Rack is a modular Ruby web server interface. Prior to versions 2.2.23, 3.1.21, and 3.2.6, Rack::Multipart::Parser extracts the boundary parameter from multipart/form-data using a greedy regular expression. When a Content-Type header contains multiple boundary parameters, Rack selects the last one rather than the first. In deployments where an upstream proxy, WAF, or intermediary interprets the first boundary parameter, this mismatch can allow an attacker to smuggle multipart content past upstream inspection and have Rack parse a different body structure than the intermediary validated. This issue has been patched in versions 2.2.23, 3.1.21, and 3.2.6.
Weakness
Product A handles inputs or steps differently than Product B, which causes A to perform incorrect actions based on its perception of B’s state.
Affected Software
| Name | Vendor | Start Version | End Version |
|---|---|---|---|
| Rack | Rack | * | 2.2.23 (excluding) |
| Rack | Rack | 3.0.0 (including) | 3.1.21 (excluding) |
| Rack | Rack | 3.2.0 (including) | 3.2.6 (excluding) |
| Ruby-rack | Ubuntu | devel | * |
| Ruby-rack | Ubuntu | esm-apps-legacy/xenial | * |
| Ruby-rack | Ubuntu | esm-apps/bionic | * |
| Ruby-rack | Ubuntu | esm-apps/focal | * |
| Ruby-rack | Ubuntu | esm-apps/jammy | * |
| Ruby-rack | Ubuntu | esm-apps/xenial | * |
| Ruby-rack | Ubuntu | esm-infra-legacy/trusty | * |
| Ruby-rack | Ubuntu | jammy | * |
| Ruby-rack | Ubuntu | noble | * |
| Ruby-rack | Ubuntu | questing | * |
| Ruby-rack | Ubuntu | resolute | * |
Related Attack Patterns
- https://cwe.mitre.org/data/definitions/105.html
- https://cwe.mitre.org/data/definitions/273.html
- https://cwe.mitre.org/data/definitions/34.html