nltk up to 3.9.2 StanfordSegmenter input validation

Summaryinfo

A vulnerability was found in nltk up to 3.9.2. It has been rated as critical. This issue affects some unknown processing of the component StanfordSegmenter Module. The manipulation leads to input validation. This vulnerability is referenced as CVE-2026-0848. Remote exploitation of the attack is possible. No exploit is available.

Detailsinfo

A vulnerability, which was classified as critical, has been found in nltk up to 3.9.2. This issue affects an unknown function of the component StanfordSegmenter Module. The manipulation with an unknown input leads to a input validation vulnerability. Using CWE to declare the problem leads to CWE-20. The product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly. Impacted is confidentiality, integrity, and availability. The summary by CVE is:

NLTK versions <=3.9.2 are vulnerable to arbitrary code execution due to improper input validation in the StanfordSegmenter module. The module dynamically loads external Java .jar files without verification or sandboxing. An attacker can supply or replace the JAR file, enabling the execution of arbitrary Java bytecode at import time. This vulnerability can be exploited through methods such as model poisoning, MITM attacks, or dependency poisoning, leading to remote code execution. The issue arises from the direct execution of the JAR file via subprocess with unvalidated classpath input, allowing malicious classes to execute when loaded by the JVM.

The advisory is shared at huntr.com. The identification of this vulnerability is CVE-2026-0848 since 01/11/2026. The exploitation is known to be easy. The attack may be initiated remotely. No form of authentication is needed for a successful exploitation. Neither technical details nor an exploit are publicly available. The price for an exploit might be around USD $0-$5k at the moment (estimation calculated on 03/10/2026).

The vulnerability scanner Nessus provides a plugin with the ID 301391 (Linux Distros Unpatched Vulnerability : CVE-2026-0848), which helps to determine the existence of the flaw in a target environment.

There is no information about possible countermeasures known. It may be suggested to replace the affected object with an alternative product.

The vulnerability is also documented in the vulnerability database at Tenable (301391). Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

Productinfo

Name

• nltk

Version

• 3.9.0
• 3.9.1
• 3.9.2

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Entryinfo

Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

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