CVE-2026-33236
In versions 3.9.3 and prior, the NLTK downloader does not validate the `subdir` and `id` attributes when processing remote XML index files.
Does this matter?
High impact if exploited, but EPSS currently rates exploitation as unlikely (0.57%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit.
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.
- CVSS 3.1
- 8.1 HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:H
- EPSS
- 0.57% probability · 46th percentile
- CISA KEV
- Not listed
- Weakness
- CWE-22
- Affected
- nltk/nltk
- Source
- security-advisories@github.com
References
- https://github.com/nltk/nltk/commit/89fe2ec2c6bae6e2e7a46dad65cc34231976ed8aPatch
- https://github.com/nltk/nltk/security/advisories/GHSA-469j-vmhf-r6v7Exploit, Vendor Advisory
- https://access.redhat.com/errata/RHSA-2026:10184
- https://access.redhat.com/errata/RHSA-2026:19712
- https://access.redhat.com/errata/RHSA-2026:37275
- https://access.redhat.com/errata/RHSA-2026:42644
- https://access.redhat.com/security/cve/CVE-2026-33236
- https://bugzilla.redhat.com/show_bug.cgi?id=2449824
- https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-33236.json
Source: NVD record, EPSS from FIRST.org, KEV from CISA. Refreshed daily.