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    CVE-2026-78683

    NLTK before 3.10.0 (affected versions <=3.9.4) contains an unsafe pickle deserialization vulnerability in the TransitionParser.parse() method (nltk/parse/transitionparser.py). The method calls pickle_load() with the default restricted=False, routing deserialization through WarningUnpickler, which does not override find_class() and therefore permits arbitrary class resolution. When an application loads an attacker-crafted model file, embedded pickle gadget chains execute arbitrary Python code with the privileges of the user running the application. NLTK provides a RestrictedUnpickler for safe deserialization, but it is not used by production code paths. Fixed in 3.10.0.

    Published:Aug 25, 2026
    Last Modified:Aug 25, 2026
    EPS:Aug 25, 2026
    EPSS Score:0.00276
    CVSS Score:9.6

    Affected Products

    Vendor
    Nltk
    Product
    Nltk

    Exploits

    https://github.com/nltk/nltk/security/advisories/GHSA-rhp5-r9x4-f5g2https://github.com/nltk/nltk/security/advisories/GHSA-rhp5-r9x4-f5g2

    Common Attack Pattern Enumeration and Classification (CAPEC)

    CAPEC-586 Object Injection

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    Common Vulnerability Scoring System

    Attack Vector
    Network
    Adjacent
    Local
    Physical
    Privileges Required
    None
    Low
    High
    User Interaction
    None
    Required
    Scope
    Unchanged
    Changed
    Confidentiality
    None
    Low
    High
    Integrity
    None
    Low
    High
    Availability
    None
    Low
    High