{"id":"CVE-2026-81722","state":"PUBLISHED","title":"nltk PorterStemmer before 3.10.3 Quadratic-time DoS","description":"nltk PorterStemmer in versions <= 3.10.2 (fixed in 3.10.3) contains an inefficient-algorithmic-complexity denial of service in PorterStemmer.stem(). The _is_consonant() helper walks backward over the entire run of trailing 'y' characters on every call, and _measure() invokes it for each stem position, causing O(n^2) behavior. A single ~20-50 KB untrusted token consisting of a long run of the letter 'y' followed by a matching suffix (e.g., 'ness') can pin a CPU core for seconds to minutes, causing availability impact.","publishedAt":"2026-08-27T14:51:15.857Z","updatedAt":"2026-08-27T17:49:54.623Z","severity":{"score":8.7,"label":"High","version":"4.0","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","source":"VulnCheck"},"assigner":"VulnCheck","products":["nltk nltk"],"affected":[{"vendor":"nltk","product":"nltk","packageURL":"pkg:pypi/nltk","defaultStatus":"unaffected","versions":[{"version":"0","status":"affected","lessThan":"3.10.3","versionType":"semver"},{"version":"3.10.3","status":"unaffected","versionType":"semver"}]}],"references":["https://github.com/nltk/nltk/security/advisories/GHSA-ww6m-cw3f-q94g","https://www.vulncheck.com/advisories/nltk-porterstemmer-before-3.10.3-quadratic-time-dos"],"weaknesses":["CWE-407"],"ingestedAt":"2026-10-29T20:13:15.269Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/81xxx/CVE-2026-81722.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-81722","state":"PUBLISHED","datePublished":"2026-08-27T14:51:15.857Z","dateUpdated":"2026-08-27T17:49:54.623Z","assignerShortName":"VulnCheck","assignerOrgId":"83251b91-4cc7-4094-a5c7-464a1b83ea10","dateReserved":"2026-08-27T11:13:14.064Z"},"containers":{"cna":{"title":"nltk PorterStemmer before 3.10.3 Quadratic-time DoS","descriptions":[{"lang":"en","value":"nltk PorterStemmer in versions <= 3.10.2 (fixed in 3.10.3) contains an inefficient-algorithmic-complexity denial of service in PorterStemmer.stem(). 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