{"id":"CVE-2026-81724","aliases":["GHSA-cw6x-m8jw-qmrh","PYSEC-2026-3739"],"url":"https://o3.security/vulnerability/CVE-2026-81724","summary":"NLTK before 3.10.3 Denial of Service via Uncontrolled Recursion","details":"NLTK before 3.10.3 contains an uncontrolled recursion vulnerability in nltk.featstruct.FeatStructReader that allows unauthenticated attackers to cause a denial of service by supplying deeply nested feature-structure input. Attackers can craft trivial payloads with nested brackets that exceed Python's recursion limit and raise an unhandled RecursionError, crashing applications that parse user-supplied feature structures or feature grammars.","published":"2026-08-27T14:51:17.358Z","modified":"2026-09-02T03:47:28.121545620Z","cvss":null,"epss":null,"cisaKev":null,"exploitsKnown":null,"affectedPackages":[{"ecosystem":"PyPI","name":"nltk","fixedVersion":"3.10.3"}],"fix":null,"references":[{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/81xxx/CVE-2026-81724.json"},{"type":"ADVISORY","url":"https://github.com/nltk/nltk/security/advisories/GHSA-cw6x-m8jw-qmrh"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-81724"},{"type":"ADVISORY","url":"https://www.vulncheck.com/advisories/nltk-before-3.10.3-denial-of-service-via-uncontrolled-recursion"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-09-02T03:47:28.121545620Z"}}