NLTK versions before 3.9.4 contain an unbounded recursion vulnerability in JSONTaggedDecoder.decode_obj() that allows attackers to cause denial of service by supplying deeply nested JSON structures. Attackers can craft JSON payloads exceeding the recursion limit to trigger an unhandled RecursionError that crashes the Python process.
Weakness
The product does not properly control the amount of recursion that takes place, consuming excessive resources, such as allocated memory or the program stack.
Affected Software
| Name | Vendor | Start Version | End Version |
|---|---|---|---|
| Nltk | Nltk | * | 3.9.4 (excluding) |
| Nltk | Ubuntu | upstream | * |