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CVE-2026-66393

CVE-2026-66393 · NLTK before 3.9.4 Denial of Service via JSONTaggedDecoder

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

NLTK versions before 3.9.4 contain an unbounded recursion vulnerability in JSONTaggedDecoder.decode_obj() that allows attackers to cause denial of service by supplying deeply nested JSON structures. Attackers can craft JSON payloads exceeding the recursion limit to trigger an unhandled RecursionError that crashes the Python process.

CVSS 8.7 · High · EPSS 0.5% · Fix available

Published
Updated

Stack: system · python

Affected products and versions

  • nltk

    Versions
    • ≥ 0, < 3.9.4: Affected (semver)
    • 3.9.4: Not affected (semver)

    Update to 3.9.4

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

    Update to 3.10.0-1

  • 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
    • 3.2
    • 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
    • 3.9b1
    Affected ranges
    • ECOSYSTEM: < 3.9.4

    Update to 3.9.4

  • 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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