UBUNTU-CVE-2026-12243

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Source
https://ubuntu.com/security/CVE-2026-12243
Import Source
https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-12243.json
JSON Data
https://api.osv.dev/v1/vulns/UBUNTU-CVE-2026-12243
Upstream
Published
2026-06-30T01:16:00Z
Modified
2026-07-01T21:19:38Z
Severity
  • 7.5 (High) CVSS_V3 - CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N CVSS Calculator
  • Ubuntu - medium
Summary
[none]
Details

NLTK version 3.9.4 is vulnerable to a path traversal attack due to an incomplete fix for GitHub Issue #3504. The _UNSAFE_NO_PROTOCOL_RE regex in nltk/data.py checks for literal ../ sequences but fails to account for percent-encoded traversal sequences such as ..%2f. The url2pathname() function decodes these sequences after the validation step, allowing an attacker to bypass the protection. This vulnerability enables an attacker to read arbitrary files accessible to the Python process by controlling the resource name parameter passed to nltk.data.load() or nltk.data.find(). The issue affects applications that rely on NLTK for resource loading, including NLP web applications, Jupyter notebooks, and CLI tools. The default pathsec.ENFORCE=False setting exacerbates the impact by not blocking the file read at the open() stage.

References

Affected packages

Ubuntu:25.10
nltk

Package

Name
nltk
Purl
pkg:deb/ubuntu/nltk?arch=source&distro=questing

Affected ranges

Type
ECOSYSTEM
Events
Introduced
0Unknown introduced version / All previous versions are affected

Affected versions

3.*
3.9.1-2

Ecosystem specific 

{
    "binaries": [
        {
            "binary_name": "python3-nltk",
            "binary_version": "3.9.1-2"
        }
    ]
}

Database specific

source 
"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-12243.json"
Ubuntu:Pro:14.04:LTS
nltk

Package

Name
nltk
Purl
pkg:deb/ubuntu/nltk?arch=source&distro=esm-infra-legacy%2Ftrusty

Affected ranges

Type
ECOSYSTEM
Events
Introduced
0Unknown introduced version / All previous versions are affected

Affected versions

2.*
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

Ecosystem specific 

{
    "binaries": [
        {
            "binary_name": "python-nltk",
            "binary_version": "2.0~b9-0ubuntu4.1~esm6"
        }
    ]
}

Database specific

source 
"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-12243.json"
Ubuntu:Pro:16.04:LTS
nltk

Package

Name
nltk
Purl
pkg:deb/ubuntu/nltk?arch=source&distro=esm-apps-legacy%2Fxenial

Affected ranges

Type
ECOSYSTEM
Events
Introduced
0Unknown introduced version / All previous versions are affected

Affected versions

3.*
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

Ecosystem specific 

{
    "binaries": [
        {
            "binary_name": "python-nltk",
            "binary_version": "3.1-1ubuntu0.1+esm4"
        },
        {
            "binary_name": "python3-nltk",
            "binary_version": "3.1-1ubuntu0.1+esm4"
        }
    ]
}

Database specific

source 
"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-12243.json"
Ubuntu:Pro:18.04:LTS
nltk

Package

Name
nltk
Purl
pkg:deb/ubuntu/nltk?arch=source&distro=esm-apps%2Fbionic

Affected ranges

Type
ECOSYSTEM
Events
Introduced
0Unknown introduced version / All previous versions are affected

Affected versions

3.*
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

Ecosystem specific 

{
    "binaries": [
        {
            "binary_name": "python-nltk",
            "binary_version": "3.2.5-1ubuntu0.1+esm4"
        },
        {
            "binary_name": "python3-nltk",
            "binary_version": "3.2.5-1ubuntu0.1+esm4"
        }
    ]
}

Database specific

source 
"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-12243.json"
Ubuntu:Pro:20.04:LTS
nltk

Package

Name
nltk
Purl
pkg:deb/ubuntu/nltk?arch=source&distro=esm-apps%2Ffocal

Affected ranges

Type
ECOSYSTEM
Events
Introduced
0Unknown introduced version / All previous versions are affected

Affected versions

3.*
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

Ecosystem specific 

{
    "binaries": [
        {
            "binary_name": "python3-nltk",
            "binary_version": "3.4.5-2ubuntu0.1~esm4"
        }
    ]
}

Database specific

source 
"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-12243.json"
Ubuntu:Pro:22.04:LTS
nltk

Package

Name
nltk
Purl
pkg:deb/ubuntu/nltk?arch=source&distro=esm-apps%2Fjammy

Affected ranges

Type
ECOSYSTEM
Events
Introduced
0Unknown introduced version / All previous versions are affected

Affected versions

3.*
3.5-1
3.6.5-1
3.6.7-1
3.7-1
3.7-1ubuntu0.1~esm1
3.7-1ubuntu0.1~esm2

Ecosystem specific 

{
    "binaries": [
        {
            "binary_name": "python3-nltk",
            "binary_version": "3.7-1ubuntu0.1~esm2"
        }
    ]
}

Database specific

source 
"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-12243.json"
Ubuntu:Pro:24.04:LTS
nltk

Package

Name
nltk
Purl
pkg:deb/ubuntu/nltk?arch=source&distro=esm-apps%2Fnoble

Affected ranges

Type
ECOSYSTEM
Events
Introduced
0Unknown introduced version / All previous versions are affected

Affected versions

3.*
3.8.1-1
3.8.1-1ubuntu0.1~esm1
3.8.1-1ubuntu0.1~esm2

Ecosystem specific 

{
    "binaries": [
        {
            "binary_name": "python3-nltk",
            "binary_version": "3.8.1-1ubuntu0.1~esm2"
        }
    ]
}

Database specific

source 
"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-12243.json"
Ubuntu:Pro:26.04:LTS
nltk

Package

Name
nltk
Purl
pkg:deb/ubuntu/nltk?arch=source&distro=esm-apps%2Fresolute

Affected ranges

Type
ECOSYSTEM
Events
Introduced
0Unknown introduced version / All previous versions are affected

Affected versions

3.*
3.9.1-2
3.9.1-2build1
3.9.2-1
3.9.2-1ubuntu0.1~esm1
3.9.2-1ubuntu0.1~esm2

Ecosystem specific 

{
    "binaries": [
        {
            "binary_name": "python3-nltk",
            "binary_version": "3.9.2-1ubuntu0.1~esm2"
        }
    ]
}

Database specific

source 
"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-12243.json"