Python-Multipart is a streaming multipart parser for Python. Prior to 0.0.30, QuerystringParser treated ; as a field separator in application/x-www-form-urlencoded bodies, in addition to &. The WHATWG URL standard, modern browsers, and Pythons urllib.parse (since the CVE-2021-23336 fix) treat only & as a separator. This creates a parser differential: the same bytes are tokenized into different fields than a WHATWG compliant intermediary would produce, allowing an attacker to smuggle extra form fields past an upstream body inspecting component. This vulnerability is fixed in 0.0.30.
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 |
|---|---|---|---|
| Python-multipart | Fastapiexpert | * | 0.0.30 (excluding) |
| Python-multipart | Ubuntu | questing | * |
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