UBUNTU-CVE-2026-81724

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Source
https://ubuntu.com/security/CVE-2026-81724
Import Source
https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-81724.json
JSON Data
https://api.osv.dev/v1/vulns/UBUNTU-CVE-2026-81724
Upstream
Published
2026-08-27T17:21:00Z
Modified
2026-09-02T16:28:28Z
Severity
  • 5.3 (Medium) CVSS_V3 - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L CVSS Calculator
  • 6.9 (Medium) CVSS_V4 - CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N CVSS Calculator
  • Ubuntu - medium
Summary
[none]
Details

NLTK before 3.10.3 contains an uncontrolled recursion vulnerability in nltk.featstruct.FeatStructReader that allows unauthenticated attackers to cause a denial of service by supplying deeply nested feature-structure input. Attackers can craft trivial payloads with nested brackets that exceed Python's recursion limit and raise an unhandled RecursionError, crashing applications that parse user-supplied feature structures or feature grammars.

References

Affected packages

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_version": "2.0~b9-0ubuntu4.1~esm6",
            "binary_name": "python-nltk"
        }
    ]
}

Database specific

source 
"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-81724.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_version": "3.1-1ubuntu0.1+esm4",
            "binary_name": "python-nltk"
        },
        {
            "binary_version": "3.1-1ubuntu0.1+esm4",
            "binary_name": "python3-nltk"
        }
    ]
}

Database specific

source 
"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-81724.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_version": "3.2.5-1ubuntu0.1+esm4",
            "binary_name": "python-nltk"
        },
        {
            "binary_version": "3.2.5-1ubuntu0.1+esm4",
            "binary_name": "python3-nltk"
        }
    ]
}

Database specific

source 
"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-81724.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_version": "3.4.5-2ubuntu0.1~esm4",
            "binary_name": "python3-nltk"
        }
    ]
}

Database specific

source 
"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-81724.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_version": "3.7-1ubuntu0.1~esm2",
            "binary_name": "python3-nltk"
        }
    ]
}

Database specific

source 
"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-81724.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_version": "3.8.1-1ubuntu0.1~esm2",
            "binary_name": "python3-nltk"
        }
    ]
}

Database specific

source 
"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-81724.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_version": "3.9.2-1ubuntu0.1~esm2",
            "binary_name": "python3-nltk"
        }
    ]
}

Database specific

source 
"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-81724.json"