Description
NLTK (Natural Language Toolkit) is a suite of open source Python modules, data sets, and tutorials supporting research and development in Natural Language Processing. In versions 3.9.3 and prior, the NLTK downloader does not validate the `subdir` and `id` attributes when processing remote XML index files. Attackers can control a remote XML index server to provide malicious values containing path traversal sequences (such as `../`), which can lead to arbitrary directory creation, arbitrary file creation, and arbitrary file overwrite. Commit 89fe2ec2c6bae6e2e7a46dad65cc34231976ed8a patches the issue.
Affected products
| Vendor | Product | Affected | Fixed |
|---|---|---|---|
| nltk | nltk | <= 3.9.3 | — |
Fixed in Linux distributions
Distributions backport fixes, so the version that fixes this vulnerability differs per release — upgrade to at least the version shown. From the distributions' security trackers and advisories.
Debian
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian 14 | nltk | 3.10.0-1 | — |
| Debian 13 | nltk | No fix yet | — |
| Debian 12 | nltk | No fix yet | — |
Ubuntu
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu 26.10 | nltk | No fix yet | — |
| Ubuntu 25.10 | nltk | No fix yet | — |
Show 7 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu Pro 26.04 LTS | nltk | 3.9.2-1ubuntu0.1~esm2 | — |
| Ubuntu Pro 24.04 LTS | nltk | 3.8.1-1ubuntu0.1~esm2 | — |
| Ubuntu Pro 22.04 LTS | nltk | 3.7-1ubuntu0.1~esm2 | — |
| Ubuntu Pro 20.04 LTS | nltk | 3.4.5-2ubuntu0.1~esm4 | — |
| Ubuntu Pro 18.04 LTS | nltk | 3.2.5-1ubuntu0.1+esm4 | — |
| Ubuntu Pro 16.04 LTS | nltk | 3.1-1ubuntu0.1+esm4 | — |
| Ubuntu Pro 14.04 LTS | nltk | 2.0~b9-0ubuntu4.1~esm6 | — |
Wolfi
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Wolfi rolling | py3-nltk +3 | 3.9.4-r0 | — |
Affected packages
| Ecosystem | Package | Affected | Fixed | Record |
|---|---|---|---|---|
| PyPI | nltk | < 3.9.4 | 3.9.4 | GHSA-469j-vmhf-r6v7 |
Advisories 1
- WID-SEC-2026-0895 IBM App Connect Enterprise: Mehrere Schwachstellen BSI CERT-Bund (WID) · Apr 19, 2026