GHSA-568f-pv23-39p4

Suggest an improvement
Source
https://github.com/advisories/GHSA-568f-pv23-39p4
Import Source
https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/09/GHSA-568f-pv23-39p4/GHSA-568f-pv23-39p4.json
JSON Data
https://api.osv.dev/v1/vulns/GHSA-568f-pv23-39p4
Aliases
Downstream
Published
2026-09-08T16:37:18Z
Modified
2026-09-08T16:45:03Z
Severity
  • 5.9 (Medium) CVSS_V3 - CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N CVSS Calculator
  • 8.2 (High) CVSS_V4 - CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N CVSS Calculator
Summary
NLTK: Stable FrameNet and NKJP readers parse outside-root XML
Details

Summary

Published nltk==3.9.4 still contains several XML-reader entrypoints that build parser paths from caller-controlled selectors or trusted-looking index state without preserving the corpus-root boundary.

Details

  • Vulnerability type: Path traversal and trusted-root bypass
  • Affected component: FramenetCorpusReader.frame_by_name, FramenetCorpusReader.doc, FramenetCorpusReader.lu, NKJPCorpusReader.header
  • Affected versions: Published 3.9.4 reproduced. Current source v3.10.0-rc2 acted as a negative control and blocked the same payloads.
  • Patched versions: Patched in version 3.10.0, which includes the path-safety rejections seen in the release candidate.
  • Root cause: Stable reader paths still construct raw XML filenames from unsafe selectors, poisoned index state, or unsafe file identifiers.

I confirmed four public stable entrypoints return parsed outside-root content: a parent-segment traversal frame name, a poisoned fulltext index filename, a poisoned LU id, and an unsafe NKJP header file identifier. Current source rejects the same payloads with explicit path-safety errors, which shows the bug is real but version-scoped to the published stable package.

PoC

Preconditions

  • The application exposes FrameNet or NKJP reader APIs while trusting NLTK to keep XML parsing inside a corpus root.

Steps

  1. Create a minimal FrameNet or NKJP corpus root and place attacker-chosen XML files outside that root.
  2. Feed unsafe selectors or poisoned index state into the relevant public stable 3.9.4 APIs.
  3. Observe frame_by_name, doc, lu(...).exemplars, or header return parsed outside-root values.
  4. Run the same payloads against current source and observe explicit path-safety rejections.

Minimal reproducible excerpt

framenet_frame_definition FRAME_LEAK
framenet_doc_text DOC_LEAK
framenet_lu_text LU_LEAK
nkjp_header_title HEADER_LEAK

Impact

Applications that process attacker-influenced FrameNet or NKJP corpus selectors or state can be made to parse XML outside the trusted corpus root through normal public reader responses.

Remediation

Keep these reader paths on the same root-confinement model as CorpusReader.open() and nltk.pathsec. Reject unsafe path components before constructing filenames from frame names, document filenames, LU ids, or NKJP file identifiers.

Resources

Database specific 
{
    "cwe_ids": [
        "CWE-22",
        "CWE-706",
        "CWE-73"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-09-08T16:37:18Z",
    "nvd_published_at": null,
    "severity": "HIGH"
}
References

Affected packages

PyPI / nltk

Package

Name
nltk
View open source insights on deps.dev
Purl
pkg:pypi/nltk

Affected ranges

Type
ECOSYSTEM
Events
Introduced
0 Unknown introduced version / All previous versions are affected
Fixed
3.10.0

Affected versions

2.*
2.0.1rc2-git
2.0b4
2.0b5
2.0b6
2.0b7
2.0b8
2.0b9
2.0.1rc1
2.0.1rc3
2.0.1rc4
2.0.1
2.0.2
2.0.3
2.0.4
2.0.5
0.*
0.8
0.9
0.9.3
0.9.4
0.9.5
0.9.6
0.9.7
0.9.8
0.9.9
3.*
3.0.0b1
3.0.0b2
3.0.0
3.0.1
3.0.2
3.0.3
3.0.4
3.0.5
3.1
3.2
3.2.1
3.2.2
3.2.3
3.2.4
3.2.5
3.3
3.4
3.4.1
3.4.2
3.4.3
3.4.4
3.4.5
3.5b1
3.5
3.6
3.6.1
3.6.2
3.6.3
3.6.4
3.6.5
3.6.6
3.6.7
3.7
3.8
3.8.1
3.9b1
3.9
3.9.1
3.9.2
3.9.3
3.9.4

Database specific

last_known_affected_version_range 
"<= 3.9.4"
source 
"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/09/GHSA-568f-pv23-39p4/GHSA-568f-pv23-39p4.json"