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CVE-2026-81725

CVE-2026-81725 · NLTK before 3.10.3 Regular Expression Denial of Service via Pl196xCorpusReader

This page contains facts from public vulnerability sources. Check the original advisory before updating.

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 read_block method through public APIs like words() and tagged_words() to force repeated rescans and achieve near-quadratic runtime growth.

CVSS 6.3 · Medium · EPSS 0.4% · Fix available

Published
Updated

Stack: system · python

Affected products and versions

  • nltk

    Versions
    • ≥ 0, < 3.10.3: Affected (semver)
    • 3.10.3: Not affected (semver)

    Update to 3.10.3

  • nltk Debian:12

    Versions
    • 3.10.0-1
    • 3.10.1-1
    • 3.10.3-1
    • 3.8-1
    • 3.8.1-1
    • 3.9.1-1
    • 3.9.1-2
    • 3.9.2-1
    • 3.9.3-1
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

  • nltk Debian:13

    Versions
    • 3.10.0-1
    • 3.10.1-1
    • 3.10.3-1
    • 3.9.1-2
    • 3.9.2-1
    • 3.9.3-1
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

  • nltk Debian:14

    Versions
    • 3.10.0-1
    • 3.10.1-1
    • 3.9.1-2
    • 3.9.2-1
    • 3.9.3-1
    Affected ranges
    • ECOSYSTEM: < 3.10.3-1

    Update to 3.10.3-1

  • nltk PyPI

    Versions
    • 0.8
    • 0.9
    • 0.9.3
    • 0.9.4
    • 0.9.5
    • 0.9.6
    • 0.9.7
    • 0.9.8
    • 0.9.9
    • 2.0.1
    • 2.0.1rc1
    • 2.0.1rc2-git
    • 2.0.1rc3
    • 2.0.1rc4
    • 2.0.2
    • 2.0.3
    • 2.0.4
    • 2.0.5
    • 2.0b4
    • 2.0b5
    • 2.0b6
    • 2.0b7
    • 2.0b8
    • 2.0b9
    • 3.0.0
    • 3.0.0b1
    • 3.0.0b2
    • 3.0.1
    • 3.0.2
    • 3.0.3
    • 3.0.4
    • 3.0.5
    • 3.1
    • 3.10.0
    • 3.10.1
    • 3.10.2
    • 3.2
    • 3.2.1
    • 3.2.2
    • 3.2.3
    • 3.2.4
    • 3.2.5
    • 3.3
    • 3.4
    • 3.4.1
    • 3.4.2
    • 3.4.3
    • 3.4.4
    • 3.4.5
    • 3.5
    • 3.5b1
    • 3.6
    • 3.6.1
    • 3.6.2
    • 3.6.3
    • 3.6.4
    • 3.6.5
    • 3.6.6
    • 3.6.7
    • 3.7
    • 3.8
    • 3.8.1
    • 3.9
    • 3.9.1
    • 3.9.2
    • 3.9.3
    • 3.9.4
    • 3.9b1
    Affected ranges
    • ECOSYSTEM: < 3.10.3

    Update to 3.10.3

  • nltk Ubuntu:Pro:14.04:LTS

    Versions
    • 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
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

  • nltk Ubuntu:Pro:16.04:LTS

    Versions
    • 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
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

  • nltk Ubuntu:Pro:18.04:LTS

    Versions
    • 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
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

  • nltk Ubuntu:Pro:20.04:LTS

    Versions
    • 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
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

  • nltk Ubuntu:Pro:22.04:LTS

    Versions
    • 3.5-1
    • 3.6.5-1
    • 3.6.7-1
    • 3.7-1
    • 3.7-1ubuntu0.1~esm1
    • 3.7-1ubuntu0.1~esm2
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

  • nltk Ubuntu:Pro:24.04:LTS

    Versions
    • 3.8.1-1
    • 3.8.1-1ubuntu0.1~esm1
    • 3.8.1-1ubuntu0.1~esm2
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

  • nltk Ubuntu:Pro:26.04:LTS

    Versions
    • 3.9.1-2
    • 3.9.1-2build1
    • 3.9.2-1
    • 3.9.2-1ubuntu0.1~esm1
    • 3.9.2-1ubuntu0.1~esm2
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

Original sources

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