CVSS 4.0
6.9 mediumCVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:N/VI:H/VA:H/SC:N/SI:N/SA:NCVE-2026-81727
Medium (6.9) in nltk nltk. EPSS 0.2% chance of exploitation in the next 30 days. Fixed in nltk 3.10.3.
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.
Severity
CVSS 3.1
7.1 highCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:H- EPSS
- 0.2% chance of exploitation in the next 30 days; higher than 8% of CVEs (scores of 2026-10-31)
- CWE
- CWE-59
- Published
- Modified
- Record from
- the NVD, synced
Affected
- nltk:nltk
Packages (OSV)
| Advisory | Ecosystem | Package | Affected | Fixed in |
|---|---|---|---|---|
| GHSA-f794-5jv7-7672 | PyPI | nltk | <3.10.3 | 3.10.3 |
| PYSEC-2026-3741 | PyPI | nltk | <3.10.3 | 3.10.3 |