CVE-2026-12243
Description
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.
Statement
A path traversal flaw was found in NLTK's resource loading functions (nltk.data.load() and nltk.data.find()). The vulnerability allows arbitrary file reads when an attacker can control the resource_name parameter by using percent-encoded path separators to bypass validation. In Red Hat products where NLTK is bundled (OpenShift AI, OpenShift Lightspeed, Ansible Automation Platform), the resource loading functions are typically used internally to load pre-packaged NLP models and corpora. Exploitation requires that untrusted user input is passed directly to these functions without additional sanitization.
Mitigation
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).
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
The following CVSS metrics and score provided are preliminary and subject to review.
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 7.5 | N/A | 7.5 |
| Attack Vector | Network | N/A | Network |
| Attack Complexity | Low | N/A | Low |
| Privileges Required | None | N/A | None |
| User Interaction | None | N/A | None |
| Scope | Unchanged | N/A | Unchanged |
| Confidentiality | High | N/A | High |
| Integrity Impact | None | N/A | None |
| Availability Impact | None | N/A | None |
Vector
Red Hat: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
cve.org: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
Understanding the Weakness (CWE)
Integrity,Confidentiality,Availability
Technical Impact: Execute Unauthorized Code or Commands
The attacker may be able to create or overwrite critical files that are used to execute code, such as programs or libraries.
Integrity
Technical Impact: Modify Files or Directories
The attacker may be able to overwrite or create critical files, such as programs, libraries, or important data. If the targeted file is used for a security mechanism, then the attacker may be able to bypass that mechanism. For example, appending a new account at the end of a password file may allow an attacker to bypass authentication.
Confidentiality
Technical Impact: Read Files or Directories
The attacker may be able read the contents of unexpected files and expose sensitive data. If the targeted file is used for a security mechanism, then the attacker may be able to bypass that mechanism. For example, by reading a password file, the attacker could conduct brute force password guessing attacks in order to break into an account on the system.
Availability
Technical Impact: DoS: Crash, Exit, or Restart
The attacker may be able to overwrite, delete, or corrupt unexpected critical files such as programs, libraries, or important data. This may prevent the product from working at all and in the case of protection mechanisms such as authentication, it has the potential to lock out product users.
Frequently Asked Questions
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