Inefficient Algorithmic Complexity 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-19639021
- published7 Sept 2026
- disclosed27 Aug 2026
- creditibfavas
Introduced: 27 Aug 2026
NewCVE-2026-81723 (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 Inefficient Algorithmic Complexity through the XMLCorpusView._read_xml_fragment() function in nltk/corpus/reader/xmldocs.py. An attacker can exhaust CPU by supplying a malformed XML corpus file with a single oversized unterminated tag to an affected reader such as BNCCorpusReader.words(). The function reads the file in 1 KiB blocks and repeatedly rescans the entire growing fragment with _VALID_XML_RE.match() and fragment.rfind("<"), so processing time grows quadratically with input size. A user opening attacker-controlled corpus data sees excessive CPU consumption and a denial of service while the reader tries to parse the file.