CVE-2019-14751: Nltk Path Traversal Vulnerability

HIGH
Advisory Identifier: GHSA-mr7p-25v2-35wr
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CVSS 7.5
CWE-22
Published
Advisory Summary

CVE-2019-14751 is a HIGH (CVSS 7.5) path traversal vulnerability (CWE-22: Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')) affecting Nltk libraries in the PyPI ecosystem. The issue involves nltk vulnerable to path traversal. Remediation is available by upgrading affected packages to version 3.4.5.

CVE-2019-14751 at a Glance

CVE Identifier CVE-2019-14751
GHSA Identifier GHSA-mr7p-25v2-35wr
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 Nltk
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:N/I:H/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 None (C:N)
Integrity High (I:H)
Availability None (A:N)

How to Fix CVE-2019-14751

To remediate this vulnerability, upgrade all affected Nltk 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: 3.4.5 
pip install nltk>=3.4.5
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 CVE-2019-14751, inspect your installed packages using pip:

pip show nltk

Analyze the terminal output to locate any version of Nltk in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 3.4.5), 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 Nltk, 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

NLTK Downloader before 3.4.5 is vulnerable to a directory traversal, allowing attackers to write arbitrary files via a `../` (dot dot slash) in an NLTK package (ZIP archive) that is mishandled during extraction.

CVE-2019-14751 Affected Nltk Versions

1 component(s)
Fixed Versions:
3.4.5
Product / Package Ecosystem Affected Versions Fixed Version
nltk
pypi/nltk
PyPI
< 3.4.5
3.4.5

References

NVD — CVE-2019-14751 NVD
https://nvd.nist.gov/vuln/detail/CVE-2019-14751
Security Fix Commit FIX COMMIT
https://github.com/nltk/nltk/commit/f59d7ed8df2e0e957f7f247fe218032abdbe9a10
GitHub Advisory / Wiki ADVISORY
https://github.com/advisories/GHSA-mr7p-25v2-35wr
Nltk Source Repository REPOSITORY
https://github.com/mssalvatore/CVE-2019-14751_PoC
Nltk Source Repository REPOSITORY
https://github.com/nltk/nltk
Nltk Source Repository REPOSITORY
https://github.com/nltk/nltk/blob/3.4.5/ChangeLog
Nltk Source Repository REPOSITORY
https://github.com/pypa/advisory-database/tree/main/vulns/nltk/PYSEC-2019-106.yaml
lists.fedoraproject.org/archives/list/packa... WEB
https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/QI4IJGLZQ5S7C5LNRNROHAO2P526XE3D
lists.fedoraproject.org/archives/list/packa... WEB
https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/ZGZSSEJH7RHH3RBUEVWWYT75QU67J7SE
Nltk Security Information SECURITY
https://salvatoresecurity.com/zip-slip-in-nltk-cve-2019-14751
Nltk Security Information SECURITY
http://lists.opensuse.org/opensuse-security-announce/2020-03/msg00054.html
Nltk Security Information SECURITY
http://lists.opensuse.org/opensuse-security-announce/2020-04/msg00001.html

Frequently Asked Questions

What is CVE-2019-14751?
CVE-2019-14751 is a security vulnerability in Nltk involving NLTK Vulnerable To Path Traversal under CWE-22: Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal').
Which Nltk versions are affected?
Affected versions include releases prior to 3.4.5 across affected packages: nltk.
What version fixes CVE-2019-14751?
Upgrading to 3.4.5 (or the latest patched release for your respective branch) resolves the vulnerability.
Is nltk affected?
Yes, nltk is affected in releases prior to 3.4.5. Upgrade your dependency to 3.4.5 or later.
What is the CVSS score of CVE-2019-14751?
CVE-2019-14751 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:N/I:H/A:N.
What CWE is associated with CVE-2019-14751?
CVE-2019-14751 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 CVE-2019-14751?
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-mr7p-25v2-35wr",
  "modified" : "2024-10-07T14:49:05Z",
  "published" : "2019-08-23T21:53:51Z",
  "aliases" : [ "CVE-2019-14751" ],
  "summary" : "NLTK Vulnerable To Path Traversal",
  "details" : "NLTK Downloader before 3.4.5 is vulnerable to a directory traversal, allowing attackers to write arbitrary files via a `../` (dot dot slash) in an NLTK package (ZIP archive) that is mishandled during extraction.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N"
  }, {
    "type" : "CVSS_V4",
    "score" : "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "PyPI",
      "name" : "nltk"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "3.4.5"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2019-14751"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/nltk/nltk/commit/f59d7ed8df2e0e957f7f247fe218032abdbe9a10"
  }, {
    "type" : "ADVISORY",
    "url" : "https://github.com/advisories/GHSA-mr7p-25v2-35wr"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/mssalvatore/CVE-2019-14751_PoC"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/nltk/nltk"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/nltk/nltk/blob/3.4.5/ChangeLog"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/pypa/advisory-database/tree/main/vulns/nltk/PYSEC-2019-106.yaml"
  }, {
    "type" : "WEB",
    "url" : "https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/QI4IJGLZQ5S7C5LNRNROHAO2P526XE3D"
  }, {
    "type" : "WEB",
    "url" : "https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/ZGZSSEJH7RHH3RBUEVWWYT75QU67J7SE"
  }, {
    "type" : "WEB",
    "url" : "https://salvatoresecurity.com/zip-slip-in-nltk-cve-2019-14751"
  }, {
    "type" : "WEB",
    "url" : "http://lists.opensuse.org/opensuse-security-announce/2020-03/msg00054.html"
  }, {
    "type" : "WEB",
    "url" : "http://lists.opensuse.org/opensuse-security-announce/2020-04/msg00001.html"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-22" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2019-08-23T21:48:38Z",
    "nvd_published_at" : "2019-08-22T16:15:00Z"
  }
}