CVE-2026-71514: Nltk Path Traversal Vulnerability

LOW
Advisory Identifier: GHSA-cv22-g7mw-8v73
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CVSS 2.5
CWE-22
Published
Advisory Summary

CVE-2026-71514 is a LOW (CVSS 2.5) 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 crubadancorpusreader path traversal allows arbitrary file disclosure. Remediation is available by upgrading affected packages to version 3.10.3.

CVE-2026-71514 at a Glance

CVE Identifier CVE-2026-71514
GHSA Identifier GHSA-cv22-g7mw-8v73
Severity LOW
CVSS v3.1 Base Score 2.5
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: 2.5

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

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

How to Fix CVE-2026-71514

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: 3.10.3 
pip install nltk>=3.10.3
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-2026-71514, 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 3.10.3), 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 3.9.4 through 3.10.2 contains a path traversal vulnerability in CrubadanCorpusReader. _load_lang_ngrams joins the corpus root with crubadan_code, the column-0 value read from the corpus table.txt mapping file, and opens the result with the builtin open() rather than the pathsec-validated opener, so os.path.join discards the root when that value is absolute and the read escapes the corpus directory without the containment check nltk.pathsec applies when ENFORCE is set. An attacker who controls a corpus package can disclose file contents outside the corpus root through lang_freq, limited to paths ending in -3grams.txt whose contents parse as token count lines.

CVE-2026-71514 Affected Nltk Versions

1 component(s)
Fixed Versions:
3.10.3
Product / Package Ecosystem Affected Versions Fixed Version
nltk
pypi/nltk
PyPI
≥ 3.9.4
< 3.10.3
3.10.3

References

NVD — CVE-2026-71514 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-71514
Security Fix Commit FIX COMMIT
https://github.com/nltk/nltk/commit/10d34b3f4fe3fec74b76527a409eb0acbac2e8ab
Nltk Source Repository REPOSITORY
https://github.com/nltk/nltk
Nltk Source Repository REPOSITORY
https://github.com/nltk/nltk/blob/v3.10.2/nltk/corpus/reader/crubadan.py#L90-L98
Nltk Release RELEASE
https://github.com/nltk/nltk/releases/tag/v3.10.3
www.vulncheck.com/advisories/nltk-thr... WEB
https://www.vulncheck.com/advisories/nltk-through-path-traversal-via-crubadancorpusreader-pathsec-bypass

Frequently Asked Questions

What is CVE-2026-71514?
CVE-2026-71514 is a security vulnerability in Nltk involving NLTK CrubadanCorpusReader path traversal allows arbitrary file disclosure 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 3.10.3 across affected packages: nltk.
What version fixes CVE-2026-71514?
Upgrading to 3.10.3 (or the latest patched release for your respective branch) resolves the vulnerability.
Is nltk affected?
Yes, nltk is affected in releases prior to 3.10.3. Upgrade your dependency to 3.10.3 or later.
What is the CVSS score of CVE-2026-71514?
CVE-2026-71514 has a CVSS v3.1 base score of 2.5 (LOW) with vector string CVSS:3.1/AV:L/AC:H/PR:N/UI:R/S:U/C:L/I:N/A:N.
What CWE is associated with CVE-2026-71514?
CVE-2026-71514 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-2026-71514?
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-cv22-g7mw-8v73",
  "modified" : "2026-09-02T15:32:28Z",
  "published" : "2026-08-22T15:31:03Z",
  "aliases" : [ "CVE-2026-71514" ],
  "summary" : "NLTK CrubadanCorpusReader path traversal allows arbitrary file disclosure",
  "details" : "NLTK 3.9.4 through 3.10.2 contains a path traversal vulnerability in CrubadanCorpusReader. _load_lang_ngrams joins the corpus root with crubadan_code, the column-0 value read from the corpus table.txt mapping file, and opens the result with the builtin open() rather than the pathsec-validated opener, so os.path.join discards the root when that value is absolute and the read escapes the corpus directory without the containment check nltk.pathsec applies when ENFORCE is set. An attacker who controls a corpus package can disclose file contents outside the corpus root through lang_freq, limited to paths ending in -3grams.txt whose contents parse as token count lines.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:L/AC:H/PR:N/UI:R/S:U/C:L/I:N/A:N"
  }, {
    "type" : "CVSS_V4",
    "score" : "CVSS:4.0/AV:L/AC:H/AT:P/PR:N/UI:P/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "PyPI",
      "name" : "nltk"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "3.9.4"
      }, {
        "fixed" : "3.10.3"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-71514"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/nltk/nltk/commit/10d34b3f4fe3fec74b76527a409eb0acbac2e8ab"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/nltk/nltk"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/nltk/nltk/blob/v3.10.2/nltk/corpus/reader/crubadan.py#L90-L98"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/nltk/nltk/releases/tag/v3.10.3"
  }, {
    "type" : "WEB",
    "url" : "https://www.vulncheck.com/advisories/nltk-through-path-traversal-via-crubadancorpusreader-pathsec-bypass"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-22" ],
    "severity" : "LOW",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-09-02T15:32:28Z",
    "nvd_published_at" : "2026-08-22T14:16:33Z"
  }
}