Improper Restriction of Recursive Entity References in DTDs ('XML Entity Expansion') Affecting nltk package, versions [,3.10.3)
Threat Intelligence
The probability is the direct output of the EPSS model, and conveys an overall sense of the threat of exploitation in the wild. The percentile measures the EPSS probability relative to all known EPSS scores. Note: This data is updated daily, relying on the latest available EPSS model version. Check out the EPSS documentation for more details.
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Test your applications- Snyk IDSNYK-PYTHON-NLTK-19256808
- published25 Aug 2026
- disclosed25 Aug 2026
- creditUnknown
Introduced: 25 Aug 2026
NewCVE-2026-78681 (opens in a new tab)How to fix?
Upgrade nltk to version 3.10.3 or higher.
Overview
nltk is a Natural Language Toolkit (NLTK) is a Python package for natural language processing.
Affected versions of this package are vulnerable to Improper Restriction of Recursive Entity References in DTDs ('XML Entity Expansion') via the raw xml.etree.ElementTree parsing in nltk.chunk.named_entity.load_ace_file, nltk.internals.ElementWrapper, and nltk.downloader’s XML loaders. An attacker can exhaust memory by supplying a crafted XML document with nested <!ENTITY> declarations that expand a few hundred bytes into megabytes when NLTK parses ACE annotation files, package metadata, or arbitrary XML strings.