CVE-2026-0848: nltk Improper Input Validation

Vulnerability summary

CVE-2026-0848 is a critical (CVSS 10.0) Improper Input Validation vulnerability in nltk. EPSS estimates a 0.77% chance of exploitation in the next 30 days, higher than 54.8% of scored vulnerabilities. 1 public exploit is recorded.

Timeline

1. 05-03-2026
   PublishedVulnerability first disclosed.
2. 06-03-2026
   Last modifiedVulnerability information updated.

Description

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.

• CWE-20Improper Input ValidationThe 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.