High 7.1Published Aug 27, 2026

CVE-2026-81727NLTK before 3.10.3 Hardlink File Overwrite via downloader

Updated under an hour ago (2026-10-19 07:30 UTC)

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No exploitation reported and no EPSS estimate yet.

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Exploited in the last 30 days

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.

CVSS: 7.1 HIGH (v3.1, CNA)CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:H
Weakness (CWE): CWE-59
Known exploited: Not in CISA's KEV catalog
EPSS (exploitation in the next 30 days): Not loaded for this CVE
Assigned by: VulnCheck
NVD analysis: Analyzed
Record last updated: Aug 27, 2026
First seen by InfoSec Signals: Oct 9, 2026

Affected products

Affected products

nltk nltk nltk:nltk (from the name)	before 3.10.3; 3.10.3 not affected	CNA record
nltk nltk nltk:nltk	before 3.10.3	NVD

References

https://github.com/nltk/nltk/security/advisories/GHSA-f794-5jv7-7672vendor-advisory, exploit
https://www.vulncheck.com/advisories/nltk-before-3.10.3-hardlink-file-overwrite-via-downloaderthird-party-advisory

The CVE record on cve.org NVD's entry

The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.