{"affected":[{"defaultStatus":"unaffected","ecosystem":"pypi","packageName":"nltk","product":"nltk","source":"CNA: VulnCheck","vendor":"nltk","versions":[{"lessThan":"3.10.4","status":"affected","version":"0","versionType":"semver"},{"status":"unaffected","version":"3.10.4","versionType":"semver"}]}],"cveId":"CVE-2026-126298","cwes":["CWE-400"],"description":"NLTK before 3.10.4 contains a denial of service vulnerability in Tree.chomsky_normal_form that allows remote attackers to exhaust CPU through quadratic-time right-factor binarization using list.pop(0). Attackers can supply a wide flat treebank tree parsed by Tree.fromstring to force tens of seconds of single-threaded CPU consumption, blocking the processing thread.","epss":null,"exploits":[],"kev":null,"metrics":[{"score":8.7,"severity":"high","source":"CNA: VulnCheck","vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N","version":"4.0"},{"score":7.5,"severity":"high","source":"CNA: VulnCheck","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","version":"3.1"},{"score":8.7,"severity":"high","source":"NVD: disclosure@vulncheck.com","vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/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","version":"4.0"},{"score":7.5,"severity":"high","source":"NVD: disclosure@vulncheck.com","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","version":"3.1"}],"modifiedAt":1794565054703,"publishedAt":1794562587213,"references":[{"source":"CNA: VulnCheck","tags":["vendor-advisory"],"url":"https://github.com/nltk/nltk/security/advisories/GHSA-r53h-rw34-8h97"},{"source":"CNA: VulnCheck","tags":["third-party-advisory"],"url":"https://www.vulncheck.com/advisories/nltk-before-3.10.4-quadratic-cpu-denial-of-service-via-tree-chomsky-normal-form"},{"source":"disclosure@vulncheck.com","tags":[],"url":"https://github.com/nltk/nltk/security/advisories/GHSA-r53h-rw34-8h97"},{"source":"disclosure@vulncheck.com","tags":[],"url":"https://www.vulncheck.com/advisories/nltk-before-3.10.4-quadratic-cpu-denial-of-service-via-tree-chomsky-normal-form"}],"remediation":[],"revision":"0c3913f674d4fc63f77b7561eefdb8e289c3470407e36748d030fba1c80da83d","sources":[{"modifiedAt":1794562587213,"name":"CNA: VulnCheck","retrievedAt":1794564582185,"url":"https://www.cve.org/CVERecord?id=CVE-2026-126298"},{"modifiedAt":1794565054703,"name":"NVD","retrievedAt":1794572185585,"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-126298"}],"ssvc":null,"status":"published","title":"NLTK before 3.10.4 Quadratic CPU Denial of Service via Tree.chomsky_normal_form","updatedAt":1794572185585}