{"id":"CVE-2026-66393","title":"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","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. Attackers can craft JSON payloads exce…","severity":"high","cvss":7.5,"cvssVector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","cwe":["CWE-674","CWE-606"],"vendor":"nltk","product":"nltk","affected":["nltk < 3.9.4"],"patched":["nltk 3.9.4"],"published":"2026-08-22","updated":"2026-10-14","sourceUpdated":"2026-10-14T13:10:00.187","source":"NVD","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2026-66393","references":[{"url":"https://github.com/nltk/nltk/security/advisories/GHSA-rf74-v2fm-23pw","label":"disclosure@vulncheck.com"},{"url":"https://www.vulncheck.com/advisories/nltk-before-denial-of-service-via-jsontaggeddecoder","label":"disclosure@vulncheck.com"},{"url":"https://github.com/nltk/nltk/security/advisories/GHSA-rf74-v2fm-23pw","label":"134c704f-9b21-4f2e-91b3-4a467353bcc0"},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-66393"},{"url":"https://github.com/nltk/nltk/commit/00cdcd392142e6c745e7120c8d50a24127df5fad"},{"url":"https://github.com/nltk/nltk"},{"url":"https://github.com/pypa/advisory-database/tree/main/vulns/nltk/PYSEC-2026-3724.yaml"},{"url":"https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-66393.json"},{"url":"https://access.redhat.com/security/cve/CVE-2026-66393"},{"url":"https://bugzilla.redhat.com/show_bug.cgi?id=2521342"},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-66393"}],"tags":["nvd","osv","pip","csaf","vex","red-hat"],"epss":0.00521,"epssPercentile":0.4405,"aliases":["GHSA-rf74-v2fm-23pw","PYSEC-2026-3724"],"ecosystem":"pip","ingestedAt":"2026-08-23T04:42:15.429Z","slug":"CVE-2026-66393","body":"## Overview\n\nNLTK 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.\n\n## Affected\n\n- `nltk < 3.9.4`\n\n## Remediation\n\nUpgrade past the affected range:\n\n- `nltk 3.9.4`\n\n## Package advisory (CVE-2026-66393)\n\nAffected packages:\n\n- `nltk < 3.9.4`\n\nPatched in:\n\n- `nltk 3.9.4`\n\nSource: https://osv.dev/vulnerability/GHSA-rf74-v2fm-23pw\n\n## Vendor advisories\n\n- **Red Hat VEX** · Important · affected: Red Hat Ansible Automation Platform 2 · no fix planned: Red Hat Ansible Automation Platform 2 · updated 2026-10-15 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-66393.json)","depth":"twilight","depthScore":41,"depthScoreParts":{"impact":41.3,"likelihood":0.1,"exploitation":0,"ransomware":0},"changes":[]}