Staging Environment: Content and features may be unstable or change without notice.
Advisory details: pypa / nltk/PYSEC-2026-2078
Advisory ID pypa/nltk/PYSEC-2026-2078
Aliases CVE-2026-54293
GHSA-p4gq-832x-fm9v
PYSEC-2026-2078
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.
Status Published
Exploitability 0.5
Weighted Severity 6.8
Risk 3.4
Affected and Fixed Packages Package Details
Introduced and Fixed Package Commit Patches Package Commit Patches Details
Weaknesses (0)
There are no known CWE.
System Score Found at
cvssv3.1 7.5 https://github.com/pypa/advisory-database/blob/main/vulns/nltk/PYSEC-2026-2078.yaml
Reference id Reference type URL
https://access.redhat.com/security/cve/CVE-2026-54293
https://bugzilla.redhat.com/show_bug.cgi?id=2491486
https://github.com/nltk/nltk/pull/3575
https://github.com/nltk/nltk/security/advisories/GHSA-p4gq-832x-fm9v
https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-54293.json
No exploits are available.

No EPSS data available for this advisory.

Patch URL
There are no known patches.
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N Found at https://github.com/pypa/advisory-database/blob/main/vulns/nltk/PYSEC-2026-2078.yaml
Attack Vector (AV) Attack Complexity (AC) Privileges Required (PR) User Interaction (UI) Scope (S) Confidentiality Impact (C) Integrity Impact (I) Availability Impact (A)

network

adjacent_network

local

physical

low

high

none

low

high

none

required

unchanged

changed

high

low

none

high

low

none

high

low

none

Vector: SSVCv2/E:P/A:Y/T:P/P:M/B:A/M:M/D:T/2026-06-22T21:18:34Z/

Decision: Track

Source URL: https://github.com/cisagov/vulnrichment/blob/develop/2026/54xxx/CVE-2026-54293.json

Source Advisory: vulnrichment/CVE-2026-54293

View SSVC decision tree 
[{'Exploitation': 'poc'},
 {'Automatable': 'yes'},
 {'Technical Impact': 'partial'},
 {'Mission Prevalence': 'minimal'},
 {'Public Well-being Impact': 'material'},
 {'Mission & Well-being': 'medium'}]