nltk — security advisory
NLTK before 3.10.3 contains a server-side request forgery vulnerability in nltk.pathsec.urlopen (and callers nltk.data.load, nltk.downloader.Downloader.index/download) when an HTTP proxy is configured. pathsec.urlopen validates the requested hostname locally, but proxy-handler inheritance disables the safe HTTP/HTTPS handlers so the actual fetch is performed by the proxy against a destination that is never re-validated. An attacker can supply a validated public URL that the proxy forwards to an internal loopback-only service, allowing disclosure of internal HTTP resources, loading of forged downloader indexes, and installation of attacker-chosen package content.
- 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-2026-78682
- Confirmed fixed CVEs
- Not specified
- Updated in this feed
- 30 Oct 2026, 09:03 UTC · Revision 1
Source evidence
NLTK before 3.10.3 contains a server-side request forgery vulnerability in nltk.pathsec.urlopen (and callers nltk.data.load, nltk.downloader.Downloader.index/download) when an HTTP proxy is configured. pathsec.urlopen validates the requested hostname locally, but proxy-handler inheritance disables the safe HTTP/HTTPS handlers so the actual fetch is performed by the proxy against a destination that is never re-validated. An attacker can supply a validated public URL that the proxy forwards to an internal loopback-only service, allowing disclosure of internal HTTP resources, loading of forged downloader indexes, and installation of attacker-chosen package content.
osv:DEBIAN-CVE-2026-78682
nltk
Fixed versions: Not specified
nltk
Fixed versions: Not specified
nltk
Fixed versions: 3.10.3-1
Complete source record
{
"id": "fc216078d6b0da1a7e659afc1f58c2df9d2b885a9a89640354730fff91da7b4e",
"url": "https://osv.dev/vulnerability/DEBIAN-CVE-2026-78682",
"method": "structured",
"payload": {
"kind": "advisory",
"title": "DEBIAN-CVE-2026-78682",
"summary": "NLTK before 3.10.3 contains a server-side request forgery vulnerability in nltk.pathsec.urlopen (and callers nltk.data.load, nltk.downloader.Downloader.index/download) when an HTTP proxy is configured. pathsec.urlopen validates the requested hostname locally, but proxy-handler inheritance disables the safe HTTP/HTTPS handlers so the actual fetch is performed by the proxy against a destination that is never re-validated. An attacker can supply a validated public URL that the proxy forwards to an internal loopback-only service, allowing disclosure of internal HTTP resources, loading of forged downloader indexes, and installation of attacker-chosen package content.",
"evidence": "osv:DEBIAN-CVE-2026-78682",
"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"
},
{
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},
{
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"evidence": "/affected/0/versions"
}
]
},
{
"name": {
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},
"prerequisites": [],
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"affected_versions": [
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"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": {
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"evidence": "/affected/2/package/name"
},
"prerequisites": [],
"fixed_versions": [
{
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"evidence": "/affected/2/ranges"
}
],
"affected_versions": [
{
"value": "3.10.0-1",
"evidence": "/affected/2/versions"
},
{
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"evidence": "/affected/2/versions"
},
{
"value": "3.9.1-2",
"evidence": "/affected/2/versions"
},
{
"value": "3.9.2-1",
"evidence": "/affected/2/versions"
},
{
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"evidence": "/affected/2/versions"
}
]
}
],
"severity": "high",
"structured": {
"id": "DEBIAN-CVE-2026-78682",
"aliases": [
"DEBIAN-CVE-2026-78682"
],
"metrics": [
{
"type": "CVSS_V4",
"score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:N/VA:N/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-2026-78682.json"
},
"ecosystem_specific": {
"urgency": "not yet assigned"
}
},
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
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"introduced": "0"
}
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}
],
"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-2026-78682.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-2026-78682.json"
},
"ecosystem_specific": {
"urgency": "not yet assigned"
}
}
],
"modified": "2026-10-13T09:47:29.234504081Z",
"provider": "osv",
"upstream": [
"CVE-2026-78682"
],
"references": [
"https://security-tracker.debian.org/tracker/CVE-2026-78682"
]
},
"related_cves": [
{
"value": "CVE-2026-78682",
"evidence": "/upstream"
}
],
"security_relevant": true,
"severity_evidence": "/severity/0/score"
},
"source_id": "core-osv",
"document_id": 307557,
"published_at": "2026-08-25T02:16:52.89+00:00"
}