GHSA-gx65-c5hj-vpv5: Duplicate Advisory Remote Code Execution Vulnerability

CRITICAL
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CVSS 9.6
CWE-502
Published
Advisory Summary

GHSA-gx65-c5hj-vpv5 is a CRITICAL (CVSS 9.6) remote code execution vulnerability (CWE-502: Deserialization of Untrusted Data) affecting Duplicate Advisory libraries in the PyPI ecosystem. The issue involves [cwe-502] unsafe pickle deserialization in transitionparser allows remote code execution. Remediation is available in the latest vendor maintenance releases.

GHSA-gx65-c5hj-vpv5 at a Glance

CVE Identifier N/A
GHSA Identifier GHSA-gx65-c5hj-vpv5
Severity CRITICAL
CVSS v3.1 Base Score 9.6
CWE Classification CWE-502: Deserialization of Untrusted Data
Affected Product Duplicate Advisory
Package Ecosystem PyPI
Published Date
Last Updated

Security Impact

CVSS: 9.6

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:H).

Attack Vector Network (AV:N)
Attack Complexity Low (AC:L)
Privileges Required None (PR:N)
User Interaction Required (UI:R)
Scope Changed (S:C)
Confidentiality High (C:H)
Integrity High (I:H)
Availability High (A:H)

How to Fix GHSA-gx65-c5hj-vpv5

To remediate this vulnerability, upgrade all affected Duplicate Advisory dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

nltk fixed: Latest secure release 
pip install nltk>=Latest secure release
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

pip show nltk

How to Check if You Are Affected

To determine whether your Python environment is affected by GHSA-gx65-c5hj-vpv5, inspect your installed packages using pip:

pip show nltk

Analyze the terminal output to locate any version of Duplicate Advisory in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than the patched release), your application is affected.

Note: The pip show nltk command checks currently installed packages in your active Python environment.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-502: Deserialization of Untrusted Data, where the product deserializes untrusted data without sufficiently ensuring that the resulting data will be valid. In Duplicate Advisory, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

## Duplicate Advisory This advisory has been withdrawn because it is a duplicate of GHSA-rhp5-r9x4-f5g2. This link is maintained to preserve external references. ## Original Description 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.

GHSA-gx65-c5hj-vpv5 Affected Duplicate Advisory Versions

1 component(s)
Product / Package Ecosystem Affected Versions Fixed Version
nltk
pypi/nltk
PyPI
≤ 3.9.4

References

GitHub Advisory / Wiki ADVISORY
https://github.com/nltk/nltk/security/advisories/GHSA-rhp5-r9x4-f5g2
NVD — GHSA-gx65-c5hj-vpv5 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-78683
www.vulncheck.com/advisories/nltk-bef... WEB
https://www.vulncheck.com/advisories/nltk-before-remote-code-execution-via-unsafe-pickle-deserialization

Frequently Asked Questions

What is GHSA-gx65-c5hj-vpv5?
GHSA-gx65-c5hj-vpv5 is a security vulnerability in Duplicate Advisory involving [CWE-502] Unsafe Pickle Deserialization in TransitionParser Allows Remote Code Execution under CWE-502: Deserialization of Untrusted Data.
Which Duplicate Advisory versions are affected?
Affected versions include releases prior to current release patches across affected packages: nltk.
What version fixes GHSA-gx65-c5hj-vpv5?
Upgrading to current release patches (or the latest patched release for your respective branch) resolves the vulnerability.
Is nltk affected?
Yes, nltk is affected in releases prior to Latest secure release. Upgrade your dependency to Latest secure release or later.
What is the CVSS score of GHSA-gx65-c5hj-vpv5?
GHSA-gx65-c5hj-vpv5 has a CVSS v3.1 base score of 9.6 (CRITICAL) with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:H.
What CWE is associated with GHSA-gx65-c5hj-vpv5?
GHSA-gx65-c5hj-vpv5 is classified under CWE-502: Deserialization of Untrusted Data (The product deserializes untrusted data without sufficiently ensuring that the resulting data will be valid.).
How can I check PyPI dependencies for GHSA-gx65-c5hj-vpv5?
Run the dependency tree command: 'pip show nltk'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-gx65-c5hj-vpv5",
  "modified" : "2026-09-02T14:40:50Z",
  "published" : "2026-08-25T03:32:11Z",
  "withdrawn" : "2026-09-02T14:40:50Z",
  "aliases" : [ ],
  "summary" : "Duplicate Advisory: [CWE-502] Unsafe Pickle Deserialization in TransitionParser Allows Remote Code Execution",
  "details" : "## Duplicate Advisory\n\nThis advisory has been withdrawn because it is a duplicate of GHSA-rhp5-r9x4-f5g2. This link is maintained to preserve external references.\n\n## Original Description\nNLTK 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.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:H"
  }, {
    "type" : "CVSS_V4",
    "score" : "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "PyPI",
      "name" : "nltk"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "last_affected" : "3.9.4"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/nltk/nltk/security/advisories/GHSA-rhp5-r9x4-f5g2"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-78683"
  }, {
    "type" : "WEB",
    "url" : "https://www.vulncheck.com/advisories/nltk-before-remote-code-execution-via-unsafe-pickle-deserialization"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-502" ],
    "severity" : "CRITICAL",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-09-02T14:40:50Z",
    "nvd_published_at" : "2026-08-25T02:16:53Z"
  }
}