PYSEC-2026-3724

vendorUSosv

view advisory published 2026-08-22Licence: CC-BY-4.0

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.

describes (1)

Related CVEs.

ID	severity	EPSS	exploitable	published
CVE-2026-66393US	high7.5	0.52% (44th)	—	2026-08-22
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 neste…

references

External citations — patches, advisories, analysis.

https://github.com/nltk/nltk/security/advisories/GHSA-rf74-v2fm-23pwEVIDENCE
https://www.vulncheck.com/advisories/nltk-before-denial-of-service-via-jsontaggeddecoderADVISORY

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