CVE-2026-109956
Description
A flaw was found in NLTK. A path traversal vulnerability in the WekaClassifier module allows an attacker to bypass directory containment restrictions by supplying unvalidated model paths. By controlling these path arguments, an attacker can write arbitrary files or probe existing files outside of permitted directories.
Statement
A moderate path traversal vulnerability was found in the Natural Language Toolkit (NLTK) WekaClassifier module, which affects Red Hat AI offerings that ship the nltk Python package, including Red Hat Lightspeed and OpenShift AI (RHOAI) components. The WekaClassifier does not validate the model_filename and model path arguments, so an attacker who can control these arguments can bypass the nltk.pathsec directory containment and cause the Weka JVM to write arbitrary files (via the -d option) or probe for existing files (via the -l option) outside of the allowed data directories. Successful exploitation requires an application to pass attacker-controlled paths to the WekaClassifier interface in an environment where the Weka JVM is available, which limits practical exposure; the impact is primarily high integrity loss through unauthorized file writes, with limited confidentiality and availability impact. While the upstream CVE record rates this flaw as Important, Red Hat classifies it as Moderate because exploitation depends on an application exposing the WekaClassifier interface to untrusted path input in a configured Weka environment. The affected Red Hat products are considered vulnerable, and a fix is being pursued through the responsible product teams.
Mitigation
Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability.
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 | N/A | 7 |
| Attack Vector | Network | N/A | Network |
| Attack Complexity | High | N/A | High |
| Privileges Required | None | N/A | None |
| User Interaction | None | N/A | None |
| Scope | Unchanged | N/A | Unchanged |
| Confidentiality | Low | N/A | Low |
| Integrity Impact | High | N/A | High |
| Availability Impact | Low | N/A | Low |
Vector
Red Hat: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:H/A:L
cve.org: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:H/A:L
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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