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.

CVSS v3 9.6 CRITICAL

9.6^/10

CVSS v3 : CRITICAL

Vector :

Exploitability : 2.8 / Impact : 6.0

Attack Vector NETWORK

Attack Complexity LOW

Privileges Required NONE

User Interaction REQUIRED

Confidentiality Impact HIGH

Integrity Impact HIGH

Availability Impact HIGH

Scope CHANGED

References

Link	Resource
https://github.com/nltk/nltk/security/advisories/GHSA-rhp5-r9x4-f5g2	Exploit Vendor Advisory
https://www.vulncheck.com/advisories/nltk-before-remote-code-execution-via-unsafe-pickle-deserialization	Third Party Advisory
https://github.com/nltk/nltk/security/advisories/GHSA-rhp5-r9x4-f5g2	Exploit Vendor Advisory

Configurations

Configuration 1 (hide)

cpe:2.3:a:nltk:nltk:*:*:*:*:*:*:*:*

History

No history.

Information

Published : 2026-08-25 02:16

Updated : 2026-08-31 19:05

NVD link : CVE-2026-78683

Mitre link : CVE-2026-78683

CVE.ORG link : CVE-2026-78683

JSON object : View

Products Affected

nltk

nltk

CWE

CWE-502

Deserialization of Untrusted Data

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