High severity7.1NVD Advisory· Published Aug 27, 2026· Updated Aug 31, 2026
CVE-2026-81727
CVE-2026-81727
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.
AI Insight
LLM-synthesized narrative grounded in this CVE's description and references.
Affected packages
Versions sourced from the GitHub Security Advisory.
| Package | Affected versions | Patched versions |
|---|---|---|
nltkPyPI | < 3.10.3 | 3.10.3 |
Affected products
4- osv-coords3 versions
< 2.7.3-r27+ 2 more
- (no CPE)range: < 2.7.3-r27
- (no CPE)range: < 0.11.3-r1
- (no CPE)range: < 0.11.3-r1
Patches
Vulnerability mechanics
References
8- github.com/nltk/nltk/security/advisories/GHSA-f794-5jv7-7672nvdExploitVendor AdvisoryWEB
- github.com/advisories/GHSA-f794-5jv7-7672ghsaADVISORY
- nvd.nist.gov/vuln/detail/CVE-2026-81727ghsaADVISORY
- www.vulncheck.com/advisories/nltk-before-3.10.3-hardlink-file-overwrite-via-downloadernvdThird Party AdvisoryWEB
- github.com/nltk/nltk/commit/9e6d5f05902b9aaa1221a0a565448d17a9c9b3e8ghsaWEB
- github.com/nltk/nltk/pull/3797ghsaWEB
- github.com/nltk/nltk/releases/tag/v3.10.3ghsaWEB
- github.com/pypa/advisory-database/tree/main/vulns/nltk/PYSEC-2026-3741.yamlghsaWEB
News mentions
1- Nltk Library: 16 Vulnerabilities Including Critical RCE Disclosed in BatchVypr Intelligence · Aug 27, 2026