CVE-2026-66393

nltk: NLTK versions before 3.9.4 contain an unbounded recursion vulnerability in JSONTaggedDecoder.decode_obj() that allows...

CVE-2026-66393 is fixed in nltk on 1 platform by DEBIAN-CVE-2026-66393 (version 3.10.0-1), released August 22, 2026. It is not reported as exploited. Patch Radar priority: Routine.

Routine

CVSS

n/a

No vendor severity

Exploitation

None reported

No vendor assessment

CISA KEV

Not listed

Not in the Known Exploited Vulnerabilities catalog

EPSS

0.0052

44th percentile

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.

Where it's fixed

Product	Fixed in	Fix	Released
Linux
nltk · Debian 14	3.10.0-1	DEBIAN-CVE-2026-66393	Aug 22, 2026

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