GHSA-q5h6-fcf5-49g9: Duplicate Advisory Remote Code Execution Vulnerability

HIGH
Share
CVSS 7.5
CWE-22
Published
Advisory Summary

GHSA-q5h6-fcf5-49g9 is a HIGH (CVSS 7.5) remote code execution vulnerability (CWE-22: Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')) affecting Duplicate Advisory libraries in the PyPI ecosystem. The issue involves arbitrary file read via path traversal in nltk.data.load() through percent-encoded sequences. Remediation is available in the latest vendor maintenance releases.

GHSA-q5h6-fcf5-49g9 at a Glance

CVE Identifier N/A
GHSA Identifier GHSA-q5h6-fcf5-49g9
Severity HIGH
CVSS v3.1 Base Score 7.5
CWE Classification CWE-22: Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')
Affected Product Duplicate Advisory
Package Ecosystem PyPI
Published Date
Last Updated

Security Impact

CVSS: 7.5

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N).

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

How to Fix GHSA-q5h6-fcf5-49g9

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-q5h6-fcf5-49g9, 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-22: Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal'), where the product uses external input to construct a pathname that is intended to identify a file or directory that is located underneath a restricted parent directory, but the product does not properly neutralize special elements within the pathname that can cause the pathname to resolve to a location that is outside of the restricted directory. 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-m42h-3232-vpv3. This link is maintained to preserve external references. ## Original Description NLTK version 3.9.4 is vulnerable to a path traversal attack due to an incomplete fix for GitHub Issue #3504. The `_UNSAFE_NO_PROTOCOL_RE` regex in `nltk/data.py` checks for literal `../` sequences but fails to account for percent-encoded traversal sequences such as `..%2f`. The `url2pathname()` function decodes these sequences after the validation step, allowing an attacker to bypass the protection. This vulnerability enables an attacker to read arbitrary files accessible to the Python process by controlling the resource name parameter passed to `nltk.data.load()` or `nltk.data.find()`. The issue affects applications that rely on NLTK for resource loading, including NLP web applications, Jupyter notebooks, and CLI tools. The default `pathsec.ENFORCE=False` setting exacerbates the impact by not blocking the file read at the `open()` stage.

GHSA-q5h6-fcf5-49g9 Affected Duplicate Advisory Versions

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

References

NVD — GHSA-q5h6-fcf5-49g9 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-12243
Duplicate Advisory Source Repository REPOSITORY
https://github.com/nltk/nltk
Duplicate Advisory Source Repository REPOSITORY
https://github.com/pypa/advisory-database/tree/main/vulns/nltk/PYSEC-2026-597.yaml
huntr.com/bounties/39aa9354-5... WEB
https://huntr.com/bounties/39aa9354-54ca-4e77-96da-580eb1fe6ed1

Frequently Asked Questions

What is GHSA-q5h6-fcf5-49g9?
GHSA-q5h6-fcf5-49g9 is a security vulnerability in Duplicate Advisory involving Arbitrary File Read via Path Traversal in nltk.data.load() through Percent-Encoded Sequences under CWE-22: Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal').
Which Duplicate Advisory versions are affected?
Affected versions include releases prior to current release patches across affected packages: nltk.
What version fixes GHSA-q5h6-fcf5-49g9?
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-q5h6-fcf5-49g9?
GHSA-q5h6-fcf5-49g9 has a CVSS v3.1 base score of 7.5 (HIGH) with vector string CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N.
What CWE is associated with GHSA-q5h6-fcf5-49g9?
GHSA-q5h6-fcf5-49g9 is classified under CWE-22: Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal') (The product uses external input to construct a pathname that is intended to identify a file or directory that is located underneath a restricted parent directory, but the product does not properly neutralize special elements within the pathname that can cause the pathname to resolve to a location that is outside of the restricted directory.).
How can I check PyPI dependencies for GHSA-q5h6-fcf5-49g9?
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-q5h6-fcf5-49g9",
  "modified" : "2026-08-13T20:44:55Z",
  "published" : "2026-06-30T03:37:14Z",
  "withdrawn" : "2026-08-13T20:44:55Z",
  "aliases" : [ ],
  "summary" : "Duplicate Advisory: Arbitrary File Read via Path Traversal in nltk.data.load() through Percent-Encoded Sequences",
  "details" : "## Duplicate Advisory\n\nThis advisory has been withdrawn because it is a duplicate of GHSA-m42h-3232-vpv3. This link is maintained to preserve external references.\n\n## Original Description\nNLTK version 3.9.4 is vulnerable to a path traversal attack due to an incomplete fix for GitHub Issue #3504. The `_UNSAFE_NO_PROTOCOL_RE` regex in `nltk/data.py` checks for literal `../` sequences but fails to account for percent-encoded traversal sequences such as `..%2f`. The `url2pathname()` function decodes these sequences after the validation step, allowing an attacker to bypass the protection. This vulnerability enables an attacker to read arbitrary files accessible to the Python process by controlling the resource name parameter passed to `nltk.data.load()` or `nltk.data.find()`. The issue affects applications that rely on NLTK for resource loading, including NLP web applications, Jupyter notebooks, and CLI tools. The default `pathsec.ENFORCE=False` setting exacerbates the impact by not blocking the file read at the `open()` stage.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "PyPI",
      "name" : "nltk"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      } ]
    } ],
    "database_specific" : {
      "last_known_affected_version_range" : "< 3.10.0"
    }
  } ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-12243"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/nltk/nltk"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/pypa/advisory-database/tree/main/vulns/nltk/PYSEC-2026-597.yaml"
  }, {
    "type" : "WEB",
    "url" : "https://huntr.com/bounties/39aa9354-54ca-4e77-96da-580eb1fe6ed1"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-22" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-08-13T20:44:55Z",
    "nvd_published_at" : "2026-06-30T01:16:29Z"
  }
}