PYSEC-2026-3748

    Dashboard / Vulnerabilities / PYSEC-2026-3748

    PYSEC-2026-3748

    Published: 25 Aug 2026Last Modified: 2 Sept 2026

    Summary:

    Details: NLTK versions before 3.10.3 use xml.etree.ElementTree to parse XML in multiple modules, which honors entity declarations in document DTDs. Attackers can craft XML payloads with nested entity declarations that expand from hundreds of bytes to megabytes in memory, causing denial of service.

    References: https://www.vulncheck.com/advisories/nltk-before-entity-expansion-dos-via-elementtree, https://github.com/nltk/nltk/security/advisories/GHSA-97qj-x29f-37w7

    Affected packages

    Package

    Name: nltk

    Purl: pkg:pypi/nltk

    Affected ranges

    Type: ECOSYSTEM

    Events:

    Introduced- 0
    Fixed -3.10.3

    Affected versions

    0.8

    Common Vulnerability Scoring System

    Attack Vector
    Network
    Adjacent
    Local
    Physical
    Privileges Required
    None
    Low
    High
    User Interaction
    None
    Required
    Scope
    Unchanged
    Changed
    Confidentiality
    None
    Low
    High
    Integrity
    None
    Low
    High
    Availability
    None
    Low
    High