CVE-2026-81725

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Source
https://cve.org/CVERecord?id=CVE-2026-81725
Import Source
https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-81725.json
JSON Data
https://api.osv.dev/v1/vulns/CVE-2026-81725
Aliases
  • GHSA-8mpw-7fpc-4gqj
Downstream
Published
2026-08-27T14:51:18.082Z
Modified
2026-08-30T03:30:14.315107571Z
Severity
  • 6.3 (Medium) CVSS_V4 - CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N CVSS Calculator
Summary
NLTK before 3.10.3 Regular Expression Denial of Service via Pl196xCorpusReader
Details

NLTK before 3.10.3 contains a regular expression denial of service vulnerability in Pl196xCorpusReader that allows attackers to cause quadratic CPU consumption by supplying malformed TEI blocks with many unmatched opening tags. Attackers can exploit lazy regex patterns in the readblock method through public APIs like words() and taggedwords() to force repeated rescans and achieve near-quadratic runtime growth.

Database specific 
{
    "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/81xxx/CVE-2026-81725.json",
    "cwe_ids": [
        "CWE-400"
    ],
    "cna_assigner": "VulnCheck"
}
References

Affected packages

Git / github.com/nltk/nltk

Affected ranges

Type
GIT
Repo
https://github.com/nltk/nltk
Events
Introduced
0 Unknown introduced commit / All previous commits are affected
Fixed
303f6e2ba8e4548a5f54fd65d86bb5c9a949f1db
Database specific
Show details 
{
    "source": [
        "AFFECTED_FIELD",
        "DESCRIPTION"
    ],
    "extracted_events": [
        {
            "introduced": "0"
        },
        {
            "fixed": "3.10.3"
        }
    ]
}

Affected versions

2.*
2.0.1rc1
2.0.1rc2
2.0.1rc3
2.0.1rc4
3.*
3.0.0b1
3.0.2
3.0.3
3.0.4
3.0.5
3.0a4
3.1
3.2
3.2.1
3.2.2
3.2.3
3.2.4
3.2.5
3.3
3.4
3.4.1
3.4.3
3.4.4
3.5
3.5b1
3.6
3.6.1
3.6.2
3.6.5
3.6.6
3.6.7
3.7
3.8
3.8.1
3.8.2
3.9
3.9.1
3.9.2
3.9.3
3.9.4
v.*
v.3.10.1
v3.*
v3.10.0
v3.10.0-rc1
v3.10.0-rc2
v3.10.1
v3.10.1-rc1
v3.10.1-rc2
v3.10.2
v3.10.2-rc1
v3.9.2

Database specific

source 
"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-81725.json"