CVE-2026-81727
NLTK before 3.10.3 Hardlink File Overwrite via downloader
MEDIUM 6.9EPSS 0.2%
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.
- Affected
- nltk
- CVSS v4.0 VULNCHECK
- 6.9 MEDIUM
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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X - CVSS v4.0 GitHub
- 6.9 MEDIUM
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 - CVSS v3.1 VULNCHECK
- 7.1 HIGH
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:H - EPSS
- 0.19% chance of exploitation in the next 30 days, 8th percentile
- Published
- 2026-08-27
Proof-of-concept exploits (1)
Security advisories
- nltk/nltk/security/advisories/GHSA-f794-5jv7-7672
- https://www.vulncheck.com/advisories/nltk-before-3.10.3-hardlink-file-overwrite-via-downl…