CVE-2026-54293

Summary

NLTK (Natural Language Toolkit) is a suite of open source Python modules, data sets, and tutorials supporting research and development in Natural Language Processing. Prior to 3.10.0-rc1, nltk.data.load() in NLTK is vulnerable to path traversal via URL-encoded path separators and traversal segments when using the nltk: URL scheme. The unsafe-path regex check is performed before url2pathname() decodes the %xx sequences (a classic decode-after-check / TOCTOU-style flaw), allowing an attacker to bypass the protection documented in NLTK's SECURITY.md and read arbitrary files from the filesystem. While literal traversal strings such as ../../../etc/passwd are correctly blocked, encoded variants such as %2fetc%2fpasswd, %2e%2e%2f…, and ..%2f..%2f slip past the regex and are subsequently decoded into a real filesystem path. This vulnerability is fixed in 3.10.0-rc1.

Affected Software

Weaknesses

• CWE-22: CWE-22: Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')

ADP Enrichment

CISA ADP Vulnrichment

• SSVC:
• Exploitation: poc
  • Automatable: yes
  • Technical Impact: partial

Additional References

• https://github.com/nltk/nltk/security/advisories/GHSA-p4gq-832x-fm9v

nltk: NLTK: Information Disclosure via Path Traversal in nltk.data.load()

Additional References

• https://access.redhat.com/security/cve/CVE-2026-54293
• https://bugzilla.redhat.com/show_bug.cgi?id=2491486
• https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-54293.json

References

• https://github.com/nltk/nltk/security/advisories/GHSA-p4gq-832x-fm9v
• https://github.com/nltk/nltk/pull/3575

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