The vulnerability of the JSONTaggedDecoder.decode_obj() function in the Natural Language Processing and symbolic processing library package allows a hacker to trigger a denial-of-service attack.

The vulnerability of the JSONTaggedDecoder.decodeobj function in the Natural Language Processing library for symbolic and statistical processing in NLTK is related to an uncontrolled recursion. Exploiting this vulnerability could allow a malicious actor to cause a service failure...

CVE-2026-66393

A flaw was found in NLTK. A remote attacker can exploit an unbounded recursion vulnerability in the JSONTaggedDecoder.decodeobj function by supplying deeply nested JSON structures. This can cause the Python process to crash, leading to a denial of service. Mitigation To mitigate this vulnerabilit...