High
nltk — security advisory
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.
- Products
- nltk
- Affected versions
- 2.0~b9-0ubuntu4, 2.0~b9-0ubuntu4.1~esm2, 2.0~b9-0ubuntu4.1~esm4, 2.0~b9-0ubuntu4.1~esm5, 2.0~b9-0ubuntu4.1~esm6, 3.0.4-1, 3.0.5-1, 3.1-1, 3.1-1ubuntu0.1, 3.1-1ubuntu0.1+esm1, 3.1-1ubuntu0.1+esm2, 3.1-1ubuntu0.1+esm3, 3.1-1ubuntu0.1+esm4, 3.10.0-1, 3.10.1-1, 3.10.3-1, 3.2.4-1, 3.2.5-1, 3.2.5-1ubuntu0.1, 3.2.5-1ubuntu0.1+esm1, 3.2.5-1ubuntu0.1+esm2, 3.2.5-1ubuntu0.1+esm3, 3.2.5-1ubuntu0.1+esm4, 3.4.5-1, 3.4.5-2, 3.4.5-2ubuntu0.1~esm1, 3.4.5-2ubuntu0.1~esm2, 3.4.5-2ubuntu0.1~esm3, 3.4.5-2ubuntu0.1~esm4, 3.5-1, 3.6.5-1, 3.6.7-1, 3.7-1, 3.7-1ubuntu0.1~esm1, 3.7-1ubuntu0.1~esm2, 3.8.1-1, 3.8.1-1ubuntu0.1~esm1, 3.8.1-1ubuntu0.1~esm2, 3.9.1-2, 3.9.1-2build1, 3.9.2-1, 3.9.2-1ubuntu0.1~esm1, 3.9.2-1ubuntu0.1~esm2, 3.9.3-1
- Fixed versions
- Not specified
- CVEs
- CVE-2026-54293
- Confirmed fixed CVEs
- Not specified
- Updated in this feed
- 31 Oct 2026, 02:45 UTC · Revision 1
Source evidence
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.
osv:UBUNTU-CVE-2026-54293
nltk
Fixed versions: Not specified
nltk
Fixed versions: Not specified
nltk
Fixed versions: Not specified
nltk
Fixed versions: Not specified
nltk
Fixed versions: Not specified
nltk
Fixed versions: Not specified
nltk
Fixed versions: Not specified
nltk
Fixed versions: Not specified
nltk
Fixed versions: Not specified
Complete source record
{
"id": "406ad5406e80fdc2bba4fd6b86c894999cbedc8dac538858743fc9ac2002d563",
"url": "https://osv.dev/vulnerability/UBUNTU-CVE-2026-54293",
"method": "structured",
"payload": {
"kind": "advisory",
"title": "UBUNTU-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.",
"evidence": "osv:UBUNTU-CVE-2026-54293",
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],
"modified": "2026-10-17T12:59:04.257405018Z",
"provider": "osv",
"upstream": [
"CVE-2026-54293"
],
"references": [
"https://ubuntu.com/security/CVE-2026-54293",
"https://www.cve.org/CVERecord?id=CVE-2026-54293",
"https://github.com/nltk/nltk/security/advisories/GHSA-p4gq-832x-fm9v",
"https://github.com/nltk/nltk/pull/3575"
]
},
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"value": "CVE-2026-54293",
"evidence": "/upstream"
}
],
"security_relevant": true,
"severity_evidence": "/severity/0/score"
},
"source_id": "core-osv",
"document_id": 359262,
"published_at": "2026-06-22T19:17:00+00:00"
}