HighFix available
nltk — security advisory
A vulnerability in NLTK versions up to and including 3.9.2 allows arbitrary file read via path traversal in multiple CorpusReader classes, including WordListCorpusReader, TaggedCorpusReader, and BracketParseCorpusReader. These classes fail to properly sanitize or validate file paths, enabling attackers to traverse directories and access sensitive files on the server. This issue is particularly critical in scenarios where user-controlled file inputs are processed, such as in machine learning APIs, chatbots, or NLP pipelines. Exploitation of this vulnerability can lead to unauthorized access to sensitive files, including system files, SSH private keys, and API tokens, and may potentially escalate to remote code execution when combined with other vulnerabilities.
- 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, 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, 3.10.0-1, 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, 3.4.5-1, 3.4.5-2, 3.4.5-2ubuntu0.1~esm1, 3.4.5-2ubuntu0.1~esm2, 3.4.5-2ubuntu0.1~esm3, 3.5-1, 3.6.5-1, 3.6.7-1, 3.7-1, 3.7-1ubuntu0.1~esm1, 3.8.1-1, 3.8.1-1ubuntu0.1~esm1, 3.9.1-2, 3.9.1-2build1, 3.9.2-1, 3.9.2-1ubuntu0.1~esm1, 3.9.3-1
- Fixed versions
- 2.0~b9-0ubuntu4.1~esm6, 3.1-1ubuntu0.1+esm4, 3.2.5-1ubuntu0.1+esm4, 3.4.5-2ubuntu0.1~esm4, 3.7-1ubuntu0.1~esm2, 3.8.1-1ubuntu0.1~esm2, 3.9.2-1ubuntu0.1~esm2
- CVEs
- CVE-2026-0847
- Confirmed fixed CVEs
- Not specified
- Updated in this feed
- 31 Oct 2026, 01:56 UTC · Revision 1
Source evidence
A vulnerability in NLTK versions up to and including 3.9.2 allows arbitrary file read via path traversal in multiple CorpusReader classes, including WordListCorpusReader, TaggedCorpusReader, and BracketParseCorpusReader. These classes fail to properly sanitize or validate file paths, enabling attackers to traverse directories and access sensitive files on the server. This issue is particularly critical in scenarios where user-controlled file inputs are processed, such as in machine learning APIs, chatbots, or NLP pipelines. Exploitation of this vulnerability can lead to unauthorized access to sensitive files, including system files, SSH private keys, and API tokens, and may potentially escalate to remote code execution when combined with other vulnerabilities.
osv:UBUNTU-CVE-2026-0847
nltk
Fixed versions: 2.0~b9-0ubuntu4.1~esm6
nltk
Fixed versions: 3.1-1ubuntu0.1+esm4
nltk
Fixed versions: 3.2.5-1ubuntu0.1+esm4
nltk
Fixed versions: 3.4.5-2ubuntu0.1~esm4
nltk
Fixed versions: 3.7-1ubuntu0.1~esm2
nltk
Fixed versions: 3.8.1-1ubuntu0.1~esm2
nltk
Fixed versions: Not specified
nltk
Fixed versions: Not specified
nltk
Fixed versions: 3.9.2-1ubuntu0.1~esm2
Complete source record
{
"id": "38252090c3f18a474e6b93557351df5eed82cdc08ad0117f61681cb23193cc5e",
"url": "https://osv.dev/vulnerability/UBUNTU-CVE-2026-0847",
"method": "structured",
"payload": {
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"title": "UBUNTU-CVE-2026-0847",
"summary": "A vulnerability in NLTK versions up to and including 3.9.2 allows arbitrary file read via path traversal in multiple CorpusReader classes, including WordListCorpusReader, TaggedCorpusReader, and BracketParseCorpusReader. These classes fail to properly sanitize or validate file paths, enabling attackers to traverse directories and access sensitive files on the server. This issue is particularly critical in scenarios where user-controlled file inputs are processed, such as in machine learning APIs, chatbots, or NLP pipelines. Exploitation of this vulnerability can lead to unauthorized access to sensitive files, including system files, SSH private keys, and API tokens, and may potentially escalate to remote code execution when combined with other vulnerabilities.",
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{
"value": "3.4.5-2ubuntu0.1~esm1",
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{
"value": "3.4.5-2ubuntu0.1~esm2",
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{
"value": "3.4.5-2ubuntu0.1~esm3",
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},
{
"name": {
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{
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"affected_versions": [
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{
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"name": {
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"name": {
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{
"value": "3.9.2-1",
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{
"value": "3.9.3-1",
"evidence": "/affected/7/versions"
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{
"value": "3.10.0-1",
"evidence": "/affected/7/versions"
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{
"value": "3.10.1-1",
"evidence": "/affected/7/versions"
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{
"value": "3.10.3-1",
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"name": {
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"value": "3.9.1-2build1",
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"aliases": [
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"package": {
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"source": "https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-0847.json"
},
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"binaries": [
{
"binary_name": "python3-nltk",
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"availability": "Available with Ubuntu Pro: https://ubuntu.com/pro"
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],
"modified": "2026-10-17T12:57:50.079574348Z",
"provider": "osv",
"upstream": [
"CVE-2026-0847"
],
"references": [
"https://ubuntu.com/security/CVE-2026-0847",
"https://www.cve.org/CVERecord?id=CVE-2026-0847",
"https://huntr.com/bounties/fc69914f-36a9-4c18-8503-10013b39f96",
"https://huntr.com/bounties/fc69914f-36a9-4c18-8503-10013b39f966",
"https://github.com/nltk/nltk/pull/3479",
"https://github.com/nltk/nltk/commit/603e34d25a2cad4612185ebfa6bc1c0dcfcfb2ab",
"https://ubuntu.com/security/notices/USN-8302-1"
]
},
"related_cves": [
{
"value": "CVE-2026-0847",
"evidence": "/upstream"
}
],
"security_relevant": true,
"severity_evidence": "/severity/0/score"
},
"source_id": "core-osv",
"document_id": 357687,
"published_at": "2026-03-04T19:16:00+00:00"
}