Advisory details:
pypa / nltk/PYSEC-2026-3741
| Advisory ID | pypa/nltk/PYSEC-2026-3741 |
| Aliases |
CVE-2026-81727
GHSA-f794-5jv7-7672 PYSEC-2026-3741 |
| Summary | 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. |
| Status | Published |
| Exploitability | 0.5 |
| Weighted Severity | 6.2 |
| Risk | 3.1 |
| Affected and Fixed Packages | Package Details |
| Introduced and Fixed Package Commit Patches | Package Commit Patches Details |
| There are no known CWE. |
| System | Score | Found at |
|---|---|---|
| cvssv4 | 6.9 | https://github.com/pypa/advisory-database/blob/main/vulns/nltk/PYSEC-2026-3741.yaml |
| Reference id | Reference type | URL |
|---|---|---|
| https://github.com/nltk/nltk/security/advisories/GHSA-f794-5jv7-7672 | ||
| https://www.vulncheck.com/advisories/nltk-before-3.10.3-hardlink-file-overwrite-via-downloader |
No EPSS data available for this advisory.
| Patch URL | |
|---|---|
| There are no known patches. | |
| Attack Vector (AV) | Attack Complexity (AC) | Attack Requirements (AT) | Privileges Required (PR) | User Interaction (UI) | Vulnerable System Impact Confidentiality (VC) | Vulnerable System Impact Integrity (VI) | Vulnerable System Impact Availability (VA) | Subsequent System Impact Confidentiality (SC) | Subsequent System Impact Integrity (SI) | Subsequent System Impact Availability (SA) |
|---|---|---|---|---|---|---|---|---|---|---|
network adjacent local physical |
low high |
none present |
none low high |
none passive active |
high low none |
high low none |
high low none |
high low none |
high low none |
high low none |
There are no SSVC decisions available.