{"cve":"CVE-2021-3828","nvd":{"published":"2021-09-27T13:15:07.993","modified":"2026-06-17T04:05:51.027","status":"Modified","description":"nltk is vulnerable to Inefficient Regular Expression Complexity","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","score":7.5},"cwes":["CWE-697","CWE-1333"],"references":["https://github.com/nltk/nltk/commit/277711ab1dec729e626b27aab6fa35ea5efbd7e6","https://huntr.dev/bounties/d19aed43-75bc-4a03-91a0-4d0bb516bc32","https://github.com/nltk/nltk/commit/277711ab1dec729e626b27aab6fa35ea5efbd7e6","https://huntr.dev/bounties/d19aed43-75bc-4a03-91a0-4d0bb516bc32"],"products":["nltk:nltk"],"source":"nvd","synced_at":"2026-10-19T21:23:41.316049955+00:00"},"epss":{"cve":"CVE-2021-3828","score":0.01592,"percentile":0.75684,"date":"2026-10-31"},"kev":null,"osv":[{"id":"GHSA-2ww3-fxvq-293j","url":"https://osv.dev/vulnerability/GHSA-2ww3-fxvq-293j","summary":"NLTK Vulnerable to REDoS","modified":"2024-10-07T15:22:59.778054Z","packages":[{"ecosystem":"PyPI","name":"nltk","purl":"pkg:pypi/nltk","ranges":["<3.6.4"],"fixed":["3.6.4"]}]},{"id":"PYSEC-2021-356","url":"https://osv.dev/vulnerability/PYSEC-2021-356","summary":"","modified":"2023-11-08T04:06:27.021117Z","packages":[{"ecosystem":"PyPI","name":"nltk","purl":"pkg:pypi/nltk","ranges":["<3.6.4"],"fixed":["3.6.4"]}]}],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}