CVE-2026-81727

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 v3 7.1 HIGH

7.1^/10

CVSS v3 : HIGH

Vector :

Exploitability : 1.8 / Impact : 5.2

Attack Vector LOCAL

Attack Complexity LOW

Privileges Required LOW

User Interaction NONE

Confidentiality Impact NONE

Integrity Impact HIGH

Availability Impact HIGH

Scope UNCHANGED

References

Link	Resource
https://github.com/nltk/nltk/security/advisories/GHSA-f794-5jv7-7672	Exploit Vendor Advisory
https://www.vulncheck.com/advisories/nltk-before-3.10.3-hardlink-file-overwrite-via-downloader	Third Party Advisory
https://github.com/nltk/nltk/security/advisories/GHSA-f794-5jv7-7672	Exploit Vendor Advisory

Configurations

Configuration 1 (hide)

cpe:2.3:a:nltk:nltk:*:*:*:*:*:*:*:*

History

No history.

Information

Published : 2026-08-27 17:21

Updated : 2026-08-31 19:08

NVD link : CVE-2026-81727

Mitre link : CVE-2026-81727

CVE.ORG link : CVE-2026-81727

JSON object : View

Products Affected

nltk

nltk

CWE

CWE-59

Improper Link Resolution Before File Access ('Link Following')

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