---
id: CVE-2026-12243
title: >-
  nltk: NLTK: Information disclosure via path traversal vulnerability
  (CVE-2026-12243)
summary: >-
  A flaw was found in NLTK. An attacker can exploit a path traversal
  vulnerability by providing specially crafted input to `nltk.data.load()` or
  `nltk.data.find()`. This allows the attacker to read arbitrary files
  accessible to the Python pr…
severity: high
cvss: 7.5
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N'
cvssSource: vendor
cwe: CWE-22
vendor: Red Hat
product: Red Hat OpenShift AI 3.4
affected:
  - exploit_intelligence
  - ansible_automation_platform 2
  - openshift_ai_rhoai
  - openshift_ai 2.25
  - openshift_ai 3.4
patched:
  - openshift_ai 2.25
  - openshift_ai 3.4
published: '2026-06-30'
updated: '2026-09-08'
sourceUpdated: '2026-09-08T21:52:26+00:00'
source: CSAF
sourceUrl: 'https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-12243.json'
references:
  - url: >-
      https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-12243.json
  - url: 'https://access.redhat.com/security/cve/CVE-2026-12243'
  - url: 'https://bugzilla.redhat.com/show_bug.cgi?id=2494748'
  - url: 'https://www.cve.org/CVERecord?id=CVE-2026-12243'
  - url: 'https://nvd.nist.gov/vuln/detail/CVE-2026-12243'
  - url: 'https://huntr.com/bounties/39aa9354-54ca-4e77-96da-580eb1fe6ed1'
  - url: 'https://access.redhat.com/errata/RHSA-2026:65126'
  - url: 'https://access.redhat.com/errata/RHSA-2026:60520'
  - url: 'https://github.com/nltk/nltk/security/advisories/GHSA-m42h-3232-vpv3'
  - url: 'https://github.com/nltk/nltk/issues/3504'
  - url: 'https://github.com/nltk/nltk/pull/3522'
  - url: >-
      https://github.com/nltk/nltk/commit/aec4fce1b84ad725b8975f7365b23a4f626572a9
  - url: >-
      https://github.com/pypa/advisory-database/tree/main/vulns/nltk/PYSEC-2026-597.yaml
  - url: >-
      https://securityinfinity.com/research/path-traversal-in-nltks-nltk-data-load-via-percent-encoded-sequences
  - url: 'https://github.com/advisories/GHSA-m42h-3232-vpv3'
tags:
  - csaf
  - vex
  - red-hat
  - exploit-available
  - ghsa
  - pip
exploits:
  github: 1
  githubRepos:
    - 'https://github.com/morzelowski/CVE-2026-12243-NLTK-PoC'
  checkedAt: '2026-09-09T03:23:21.292Z'
exploitAvailable: true
aliases:
  - GHSA-m42h-3232-vpv3
ecosystem: pip
ingestedAt: '2026-08-13T21:07:31.849Z'
---

## Overview

A flaw was found in NLTK. An attacker can exploit a path traversal vulnerability by providing specially crafted input to `nltk.data.load()` or `nltk.data.find()`. This allows the attacker to read arbitrary files accessible to the Python process, leading to information disclosure. The vulnerability arises from an incomplete fix that fails to account for percent-encoded traversal sequences.

## Vendor advisories

- **RHSA-2026:65126** · Red Hat · fixed in: Red Hat OpenShift AI 2.25 · released 2026-09-08 · [advisory](https://access.redhat.com/errata/RHSA-2026:65126)
- **RHSA-2026:60520** · Red Hat · fixed in: Red Hat OpenShift AI 3.4 · released 2026-08-27 · [advisory](https://access.redhat.com/errata/RHSA-2026:60520)
- **Red Hat VEX** · Important · affected: Exploit Intelligence, Red Hat Ansible Automation Platform 2, Red Hat OpenShift AI (RHOAI) · no fix planned: Red Hat Ansible Automation Platform 2, Exploit Intelligence, Red Hat OpenShift AI (RHOAI) · updated 2026-09-08 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-12243.json)

**nltk: NLTK: Information disclosure via path traversal vulnerability** — rated Important by Red Hat. Released 2026-06-30, updated 2026-09-08.

Affected:

- Exploit Intelligence
- Red Hat Ansible Automation Platform 2
- Red Hat OpenShift AI (RHOAI)

Fixed:

- Red Hat OpenShift AI 2.25
- Red Hat OpenShift AI 3.4

No fix planned:

- Red Hat Ansible Automation Platform 2
- Exploit Intelligence
- Red Hat OpenShift AI (RHOAI)

Not affected:

- Red Hat OpenShift AI 2.25
- Red Hat OpenShift AI 3.4
- OpenShift Lightspeed
- Red Hat OpenShift AI (RHOAI)

## Remediation

For Red Hat OpenShift AI 2.25.11 see the following documentation, which will be updated shortly for this release, for important instructions on how to upgrade your cluster and fully apply this errata update:

https://docs.redhat.com/en/documentation/red_hat_openshift_ai/ https://access.redhat.com/errata/RHSA-2026:65126
For Red Hat OpenShift AI 3.4.4 see the following documentation, which will be updated shortly for this release, for important instructions on how to upgrade your cluster and fully apply this errata update:

https://docs.redhat.com/en/documentation/red_hat_openshift_ai/ https://access.redhat.com/errata/RHSA-2026:60520

Workarounds / mitigations:

- Do not pass untrusted or user-controlled input directly to nltk.data.load() or nltk.data.find(). Validate and sanitize any resource name parameter before use, rejecting values containing percent-encoded characters (%2f, %2e) or path traversal sequences. As defense-in-depth, set nltk.pathsec.ENFORCE = True in application code to enable file-read restrictions at the open stage (disabled by default).

## Package advisory (CVE-2026-12243)

Affected packages:

- `nltk < 3.10.0`

Patched in:

- `nltk 3.10.0`

Source: https://github.com/advisories/GHSA-m42h-3232-vpv3