HighFix available
nltk — security advisory
NLTK versions before 3.10.3 use xml.etree.ElementTree to parse XML in multiple modules, which honors entity declarations in document DTDs. Attackers can craft XML payloads with nested entity declarations that expand from hundreds of bytes to megabytes in memory, causing denial of service.
- 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
- 3.10.3-1
- CVEs
- CVE-2026-78681
- Confirmed fixed CVEs
- Not specified
- Updated in this feed
- 30 Oct 2026, 09:03 UTC · Revision 1
Source evidence
NLTK versions before 3.10.3 use xml.etree.ElementTree to parse XML in multiple modules, which honors entity declarations in document DTDs. Attackers can craft XML payloads with nested entity declarations that expand from hundreds of bytes to megabytes in memory, causing denial of service.
osv:DEBIAN-CVE-2026-78681
nltk
Fixed versions: Not specified
nltk
Fixed versions: Not specified
nltk
Fixed versions: 3.10.3-1
Complete source record
{
"id": "de00550306a7da4ebb712622b60a8e1f848a5cfaf2011a79b7b32a52ced1e971",
"url": "https://osv.dev/vulnerability/DEBIAN-CVE-2026-78681",
"method": "structured",
"payload": {
"kind": "advisory",
"title": "DEBIAN-CVE-2026-78681",
"summary": "NLTK versions before 3.10.3 use xml.etree.ElementTree to parse XML in multiple modules, which honors entity declarations in document DTDs. Attackers can craft XML payloads with nested entity declarations that expand from hundreds of bytes to megabytes in memory, causing denial of service.",
"evidence": "osv:DEBIAN-CVE-2026-78681",
"products": [
{
"name": {
"value": "nltk",
"evidence": "/affected/0/package/name"
},
"prerequisites": [],
"fixed_versions": [],
"affected_versions": [
{
"value": "3.10.0-1",
"evidence": "/affected/0/versions"
},
{
"value": "3.10.1-1",
"evidence": "/affected/0/versions"
},
{
"value": "3.10.3-1",
"evidence": "/affected/0/versions"
},
{
"value": "3.8-1",
"evidence": "/affected/0/versions"
},
{
"value": "3.8.1-1",
"evidence": "/affected/0/versions"
},
{
"value": "3.9.1-1",
"evidence": "/affected/0/versions"
},
{
"value": "3.9.1-2",
"evidence": "/affected/0/versions"
},
{
"value": "3.9.2-1",
"evidence": "/affected/0/versions"
},
{
"value": "3.9.3-1",
"evidence": "/affected/0/versions"
}
]
},
{
"name": {
"value": "nltk",
"evidence": "/affected/1/package/name"
},
"prerequisites": [],
"fixed_versions": [],
"affected_versions": [
{
"value": "3.10.0-1",
"evidence": "/affected/1/versions"
},
{
"value": "3.10.1-1",
"evidence": "/affected/1/versions"
},
{
"value": "3.10.3-1",
"evidence": "/affected/1/versions"
},
{
"value": "3.9.1-2",
"evidence": "/affected/1/versions"
},
{
"value": "3.9.2-1",
"evidence": "/affected/1/versions"
},
{
"value": "3.9.3-1",
"evidence": "/affected/1/versions"
}
]
},
{
"name": {
"value": "nltk",
"evidence": "/affected/2/package/name"
},
"prerequisites": [],
"fixed_versions": [
{
"value": "3.10.3-1",
"evidence": "/affected/2/ranges"
}
],
"affected_versions": [
{
"value": "3.10.0-1",
"evidence": "/affected/2/versions"
},
{
"value": "3.10.1-1",
"evidence": "/affected/2/versions"
},
{
"value": "3.9.1-2",
"evidence": "/affected/2/versions"
},
{
"value": "3.9.2-1",
"evidence": "/affected/2/versions"
},
{
"value": "3.9.3-1",
"evidence": "/affected/2/versions"
}
]
}
],
"severity": "high",
"structured": {
"id": "DEBIAN-CVE-2026-78681",
"aliases": [
"DEBIAN-CVE-2026-78681"
],
"metrics": [
{
"type": "CVSS_V4",
"score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/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"
}
],
"affected": [
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "0"
}
]
}
],
"package": {
"name": "nltk",
"purl": "pkg:deb/debian/nltk?arch=source&distro=bookworm",
"ecosystem": "Debian:12"
},
"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"
],
"database_specific": {
"source": "https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2026-78681.json"
},
"ecosystem_specific": {
"urgency": "not yet assigned"
}
},
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "0"
}
]
}
],
"package": {
"name": "nltk",
"purl": "pkg:deb/debian/nltk?arch=source&distro=trixie",
"ecosystem": "Debian:13"
},
"versions": [
"3.10.0-1",
"3.10.1-1",
"3.10.3-1",
"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-2026-78681.json"
},
"ecosystem_specific": {
"urgency": "not yet assigned"
}
},
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "0"
},
{
"fixed": "3.10.3-1"
}
]
}
],
"package": {
"name": "nltk",
"purl": "pkg:deb/debian/nltk?arch=source&distro=forky",
"ecosystem": "Debian:14"
},
"versions": [
"3.10.0-1",
"3.10.1-1",
"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-2026-78681.json"
},
"ecosystem_specific": {
"urgency": "not yet assigned"
}
}
],
"modified": "2026-10-13T09:47:29.652343990Z",
"provider": "osv",
"upstream": [
"CVE-2026-78681"
],
"references": [
"https://security-tracker.debian.org/tracker/CVE-2026-78681"
]
},
"related_cves": [
{
"value": "CVE-2026-78681",
"evidence": "/upstream"
}
],
"security_relevant": true,
"severity_evidence": "/severity/0/score"
},
"source_id": "core-osv",
"document_id": 307558,
"published_at": "2026-08-25T02:16:52.75+00:00"
}