{"schemaVersion":3,"id":"GHSA-PF76-Q698-37V8","aliases":[],"status":"published","duplicateOf":null,"title":null,"description":"Duplicate Advisory: Uncontrolled recursion in nltk.featstruct.FeatStructReader causes unhandled RecursionError (DoS) via deeply nested feature-structure input\n\n## Duplicate Advisory\n\nThis advisory has been withdrawn because it is a duplicate of GHSA-cw6x-m8jw-qmrh. This link is maintained to preserve external references.\n\n## Original Description\nNLTK 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.","dates":{"published":"2026-08-27T18:32:30.000Z","modified":"2026-09-10T03:50:53.771Z","reserved":null,"kevAdded":[],"kevDue":[]},"cvss":{"headline":{"score":6.9,"severity":"medium","version":"4.0","versionLabel":"v4.0","source":"OSV · Pypi","vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X","computed":true,"selection":"version-preference"},"metrics":[{"version":"4.0","versionLabel":"v4.0","source":"OSV · Pypi","score":6.9,"severity":"medium","vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X","exploitability":null,"impact":null,"computed":true},{"version":"3.1","versionLabel":"v3.1","source":"OSV · Pypi","score":5.3,"severity":"medium","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L","exploitability":10,"impact":2.3,"computed":true}]},"epss":{"probability":null,"percentile":null,"severity":"unknown","asOf":null,"change":{"pp":null,"baselineDate":null,"baselineScore":null},"history":[],"last30":[]},"kev":{"state":"not-listed","entries":[],"listedCount":0,"totalCatalogs":3,"catalogs":[{"source":"cisa","label":"CISA","listed":false,"entry":null},{"source":"enisa","label":"ENISA","listed":false,"entry":null},{"source":"circl","label":"CIRCL","listed":false,"entry":null}]},"ransomware":{"state":"none-recorded","sources":[]},"exploits":[],"exploitCount":0,"weaknesses":[],"affected":[{"vendor":"PyPI","product":"nltk","name":"nltk","label":"nltk","ecosystem":"PyPI","cpePart":null,"purl":"pkg:pypi/nltk","purlType":"pypi","versions":[{"text":"≤ 3.10.2","noFixRecorded":false,"fixedIn":null}],"versionsText":"≤ 3.10.2","eol":null,"hubHref":null}],"affectedCount":1,"eol":{"hasEol":false,"count":0},"references":[{"url":"https://github.com/nltk/nltk/security/advisories/GHSA-cw6x-m8jw-qmrh","label":"github.com/nltk/nltk/security/advisories/GHSA-cw6x-m8jw-qmrh","hostname":"github.com","tags":["WEB"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-81724","label":"nvd.nist.gov/vuln/detail/CVE-2026-81724","hostname":"nvd.nist.gov","tags":["Advisory"]},{"url":"https://www.vulncheck.com/advisories/nltk-before-3.10.3-denial-of-service-via-uncontrolled-recursion","label":"www.vulncheck.com/advisories/nltk-before-3.10.3-denial-of-service-via-uncontrolled-recursion","hostname":"www.vulncheck.com","tags":["WEB"]}],"lineage":{"upstream":[],"downstream":["CVE-2026-81724"],"duplicates":[],"related":["CGA-JCFJ-CJGW-XC3R"]},"timeline":[{"kind":"published","date":"2026-08-27T18:32:30.000Z","label":"Published","detail":"Vulnerability first disclosed.","source":null},{"kind":"modified","date":"2026-09-10T03:50:53.771Z","label":"Last modified","detail":"Vulnerability information updated.","source":null}],"risk":{"score":28,"level":"medium","profile":"Default","thresholds":{"critical":75,"high":50,"medium":25,"low":10}},"meta":{"dataAsOf":"2026-10-21T19:12:59.639Z","stale":false,"partial":false}}