{"id":"CVE-2026-81727","summary":"NLTK before 3.10.3 Hardlink File Overwrite via downloader","details":"NLTK versions before 3.10.3 contain a filesystem containment bypass vulnerability in the Downloader.download and Downloader.incr_download methods that allows attackers to overwrite files outside the install root through pre-existing hardlinks. Attackers with write access to a shared downloader directory can create hardlinks pointing to outside-root files that are then overwritten during normal package extraction, mutating files outside the intended install tree.","aliases":["GHSA-f794-5jv7-7672"],"modified":"2026-08-30T03:30:44.428292407Z","published":"2026-08-27T14:51:19.564Z","database_specific":{"cna_assigner":"VulnCheck","cwe_ids":["CWE-59"],"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/81xxx/CVE-2026-81727.json"},"references":[{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/81xxx/CVE-2026-81727.json"},{"type":"ADVISORY","url":"https://github.com/nltk/nltk/security/advisories/GHSA-f794-5jv7-7672"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-81727"},{"type":"ADVISORY","url":"https://www.vulncheck.com/advisories/nltk-before-3.10.3-hardlink-file-overwrite-via-downloader"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://github.com/nltk/nltk","events":[{"introduced":"0"},{"fixed":"303f6e2ba8e4548a5f54fd65d86bb5c9a949f1db"}],"database_specific":{"source":["AFFECTED_FIELD","DESCRIPTION"],"extracted_events":[{"introduced":"0"},{"fixed":"3.10.3"}]}}],"versions":["v3.10.2-rc1","v3.10.2","v3.10.1","v.3.10.1","v3.10.1-rc2","v3.10.0-rc2","v3.10.0","v3.10.1-rc1","v3.10.0-rc1","3.9.4","3.9.3","v3.9.2","3.9.2","3.9.1","3.9","3.8.2","3.8.1","3.8","3.7","3.6.7","3.6.6","3.6.5","3.6.2","3.6.1","3.6","3.5","3.5b1","3.4.4","3.4.3","3.4.1","3.4","3.3","3.2.5","3.2.4","3.2.3","3.2.2","3.2.1","3.2","3.1","3.0.5","3.0.4","3.0.3","3.0.2","3.0.0b1","3.0a4","2.0.1rc4","2.0.1rc3","2.0.1rc2","2.0.1rc1"],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-81727.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V4","score":"CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:N/VI:H/VA:H/SC:N/SI:N/SA:N"}]}