nltk — security advisory
NLTK (Natural Language Toolkit) before version 3.9.3 contains an eval injection vulnerability in the nltk.collocations module that allows an attacker who controls command-line arguments to execute arbitrary Python code. When collocations.py is invoked directly, the __main__ block passes command-line arguments directly to eval() as suffixes of BigramAssocMeasures without allowlist validation or sanitization, enabling an attacker to supply a Python expression that escapes the intended attribute lookup and executes arbitrary code including OS commands via the os module.
- Products
- nltk
- Affected versions
- 3.10.0-1, 3.10.1-1, 3.10.3-1, 3.8-1, 3.8.1-1, 3.9.1-1, 3.9.1-2, 3.9.2-1, 3.9.3-1
- Fixed versions
- 3.9.3-1
- CVEs
- CVE-2025-71408
- Confirmed fixed CVEs
- Not specified
- Updated in this feed
- 28 Oct 2026, 11:07 UTC · Revision 1
Source evidence
NLTK (Natural Language Toolkit) before version 3.9.3 contains an eval injection vulnerability in the nltk.collocations module that allows an attacker who controls command-line arguments to execute arbitrary Python code. When collocations.py is invoked directly, the __main__ block passes command-line arguments directly to eval() as suffixes of BigramAssocMeasures without allowlist validation or sanitization, enabling an attacker to supply a Python expression that escapes the intended attribute lookup and executes arbitrary code including OS commands via the os module.
osv:DEBIAN-CVE-2025-71408
nltk
Fixed versions: Not specified
nltk
Fixed versions: Not specified
nltk
Fixed versions: 3.9.3-1
Complete source record
{
"id": "600515d2051aa7962ff9e4b2c452653d1b5a05e0232cd94453dd1b9f4918176f",
"url": "https://osv.dev/vulnerability/DEBIAN-CVE-2025-71408",
"method": "structured",
"payload": {
"kind": "advisory",
"title": "DEBIAN-CVE-2025-71408",
"summary": "NLTK (Natural Language Toolkit) before version 3.9.3 contains an eval injection vulnerability in the nltk.collocations module that allows an attacker who controls command-line arguments to execute arbitrary Python code. When collocations.py is invoked directly, the __main__ block passes command-line arguments directly to eval() as suffixes of BigramAssocMeasures without allowlist validation or sanitization, enabling an attacker to supply a Python expression that escapes the intended attribute lookup and executes arbitrary code including OS commands via the os module.",
"evidence": "osv:DEBIAN-CVE-2025-71408",
"products": [
{
"name": {
"value": "nltk",
"evidence": "/affected/0/package/name"
},
"prerequisites": [],
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"affected_versions": [
{
"value": "3.10.0-1",
"evidence": "/affected/0/versions"
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{
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"evidence": "/affected/0/versions"
},
{
"value": "3.10.3-1",
"evidence": "/affected/0/versions"
},
{
"value": "3.8-1",
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},
{
"value": "3.8.1-1",
"evidence": "/affected/0/versions"
},
{
"value": "3.9.1-1",
"evidence": "/affected/0/versions"
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{
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"evidence": "/affected/0/versions"
},
{
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{
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{
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{
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],
"severity": "high",
"structured": {
"id": "DEBIAN-CVE-2025-71408",
"aliases": [
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"metrics": [
{
"type": "CVSS_V4",
"score": "CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X"
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"affected": [
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"package": {
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"purl": "pkg:deb/debian/nltk?arch=source&distro=bookworm",
"ecosystem": "Debian:12"
},
"versions": [
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"3.10.1-1",
"3.10.3-1",
"3.8-1",
"3.8.1-1",
"3.9.1-1",
"3.9.1-2",
"3.9.2-1",
"3.9.3-1"
],
"database_specific": {
"source": "https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2025-71408.json"
},
"ecosystem_specific": {
"urgency": "not yet assigned"
}
},
{
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"package": {
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"ecosystem": "Debian:13"
},
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],
"database_specific": {
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},
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}
},
{
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],
"package": {
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"purl": "pkg:deb/debian/nltk?arch=source&distro=forky",
"ecosystem": "Debian:14"
},
"versions": [
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],
"database_specific": {
"source": "https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2025-71408.json"
},
"ecosystem_specific": {
"urgency": "not yet assigned"
}
}
],
"modified": "2026-10-09T09:47:29.862523027Z",
"provider": "osv",
"upstream": [
"CVE-2025-71408"
],
"references": [
"https://security-tracker.debian.org/tracker/CVE-2025-71408"
]
},
"related_cves": [
{
"value": "CVE-2025-71408",
"evidence": "/upstream"
}
],
"security_relevant": true,
"severity_evidence": "/severity/0/score"
},
"source_id": "core-osv",
"document_id": 111576,
"published_at": "2026-07-24T22:16:50.063+00:00"
}