CVE-2026-81727
NLTK before 3.10.3 Hardlink File Overwrite via downloader
- State
- Published
- Severity
- 6.9 Medium
- Published
- Aug 27, 2026
- Updated
- Aug 27, 2026
- Reserved
- Aug 27, 2026
Description
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.
Scores
| CVSS | Score | Vector | Source |
|---|---|---|---|
| 4.0 | 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 | VulnCheck |
| 3.1 | 7.1 High | CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:H | VulnCheck |
Weaknesses
- CWE-59 Improper Link Resolution Before File Access ('Link Following')
Affected Products
| Product | Versions |
|---|---|
nltknltk |
|
References
- GitHub Security Advisory (GHSA-f794-5jv7-7672)vendor-advisory
- VulnCheck Advisory: NLTK before 3.10.3 Hardlink File Overwrite via downloaderthird-party-advisory
Every record here comes from the CVE Program’s CVE List. © 1999–2026 The MITRE Corporation. CVE is a registered trademark of The MITRE Corporation. The records are reproduced under the CVE Program terms of use.