Staging Environment: Content and features may be unstable or change without notice.
Advisory details: gitlab / pypi/nltk/CVE-2026-81727
Advisory ID gitlab/pypi/nltk/CVE-2026-81727
Aliases CVE-2026-81727
GHSA-f794-5jv7-7672
Summary NLTK: Downloader.download follows hardlinks and overwrites outside-root files NLTK's downloader now blocks symlink escapes during ZIP extraction, but it still treats pre-existing hardlinks inside the install tree as ordinary in-root files. A normal package install can therefore overwrite an outside-root inode through that hardlink.
Status Published
Exploitability 0.5
Weighted Severity 0.0
Risk
Affected and Fixed Packages Package Details
Introduced and Fixed Package Commit Patches Package Commit Patches Details
Weaknesses (5)
CWE-73 External Control of File Name or Path
CWE-59 Improper Link Resolution Before File Access ('Link Following')
CWE-61 UNIX Symbolic Link (Symlink) Following
CWE-937 OWASP Top Ten 2013 Category A9 - Using Components with Known Vulnerabilities
CWE-1035 OWASP Top Ten 2017 Category A9 - Using Components with Known Vulnerabilities
System Score Found at
cvssv3.1 https://gitlab.com/gitlab-org/advisories-community/-/blob/main/pypi/nltk/CVE-2026-81727.yml
Reference id Reference type URL
https://github.com/nltk/nltk/commit/9e6d5f05902b9aaa1221a0a565448d17a9c9b3e8
https://github.com/nltk/nltk/pull/3797
https://github.com/nltk/nltk/releases/tag/v3.10.3
https://github.com/nltk/nltk/security/advisories/GHSA-f794-5jv7-7672
https://github.com/pypa/advisory-database/tree/main/vulns/nltk/PYSEC-2026-3741.yaml
https://www.vulncheck.com/advisories/nltk-before-3.10.3-hardlink-file-overwrite-via-downloader
CVE-2026-81727 https://nvd.nist.gov/vuln/detail/CVE-2026-81727
GHSA-f794-5jv7-7672 https://github.com/advisories/GHSA-f794-5jv7-7672
No exploits are available.

No EPSS data available for this advisory.

Patch URL
There are no known patches.
Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:H Found at https://gitlab.com/gitlab-org/advisories-community/-/blob/main/pypi/nltk/CVE-2026-81727.yml
Attack Vector (AV) Attack Complexity (AC) Privileges Required (PR) User Interaction (UI) Scope (S) Confidentiality Impact (C) Integrity Impact (I) Availability Impact (A)

network

adjacent_network

local

physical

low

high

none

low

high

none

required

unchanged

changed

high

low

none

high

low

none

high

low

none

There are no SSVC decisions available.