{"action":"Upgrade nltk to 3.9.4 or later.","affected":[{"fixed":"3.9.4","introduced":"0"}],"component":"nltk","cve_ids":["CVE-2026-66393"],"ecosystem":"PyPI","epss":0.00521,"exploited":false,"fixed_versions":["3.9.4"],"ghsa_id":"GHSA-rf74-v2fm-23pw","id":"tcs_01M5KH6ZK2PPVCM6XHNPQYGENG","modified_at":"2026-08-28T02:30:02.708784842Z","published_at":"2026-08-22T15:16:19.633Z","references":["https://osv.dev/vulnerability/PYSEC-2026-3724","https://www.vulncheck.com/advisories/nltk-before-denial-of-service-via-jsontaggeddecoder","https://github.com/nltk/nltk/security/advisories/GHSA-rf74-v2fm-23pw"],"severity":{"label":"unknown"},"sources":[{"source":"osv","source_id":"PYSEC-2026-3724","url":"https://osv.dev/vulnerability/PYSEC-2026-3724"}],"summary":"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. A"}