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.

There are packages installed that are affected by a vulnerability referenced in the following CVE:

  - 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. (CVE-2026-78683)

The Linux/Unix host has one or more packages installed that are impacted by a vulnerability without a vendor supplied patch available.

  - 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. (CVE-2026-78683)

Note that Nessus relies on the presence of the package as reported by the vendor.

ID	Name	Product	Family	Type	Severity
459929	Echo: nltk: security update to 3.10.0	Tenable Cloud Security	Echo Local Security Checks	Local	critical
459929	Echo: nltk: security update to 3.10.0	Tenable Self-Hosted Container Security	Echo Local Security Checks	Local	critical
339444	Linux Distros Unpatched Vulnerability : CVE-2026-78683	Nessus	Misc.	Local	critical

Detections

Analytics

CVE-2026-78683

critical

Tenable Plugins

critical

critical

critical