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.
Scoring
- Severity
- MEDIUM
- CVSS base score
- 7.1
- CVSS vector
- 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
- EPSS probability
- 0.14%
- CWE
- CWE-59
- Published
- 2026-08-27
- Last modified
- 2026-08-27
Affected products
- nltk nltk
- nltk nltk
Weakness type
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