p PatchFirst

CVE-2026-33349

CVE-2026-33349 · fast-xml-parser: Entity Expansion Limits Bypassed When Set to Zero Due to JavaScript Falsy Evaluation

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

fast-xml-parser allows users to process XML from JS object without C/C++ based libraries or callbacks. From version 4.0.0-beta.3 to before version 5.5.7, the DocTypeReader in fast-xml-parser uses JavaScript truthy checks to evaluate maxEntityCount and maxEntitySize configuration limits. When a developer explicitly sets either limit to 0 — intending to disallow all entities or restrict entity size to zero bytes — the falsy nature of 0 in JavaScript causes the guard conditions to short-circuit, completely bypassing the limits. An attacker who can supply XML input to such an application can trigger unbounded entity expansion, leading to memory exhaustion and denial of service. This issue has been patched in version 5.5.7.

CVSS 5.9 · Medium · EPSS 0.5% · Fix available

Published
Updated

Stack: system · node

Affected products and versions

  • fast-xml-parser

    Versions
    • >= 4.0.0-beta.3, < 5.5.7: Affected

    No fix published

  • node-webfont Debian:12

    Versions
    • 11.4.0+dfsg2+~cs35.7.26-10
    • 11.4.0+dfsg2+~cs35.7.26-11
    • 11.4.0+dfsg2+~cs35.7.26-12
    • 11.4.0+dfsg2+~cs35.7.26-13
    • 11.4.0+dfsg2+~cs35.7.26-14
    • 11.4.0+dfsg2+~cs35.7.26-15
    • 11.4.0+dfsg2+~cs35.7.26-16
    • 11.4.0+dfsg2+~cs35.7.26-18
    • 11.4.0+dfsg2+~cs35.7.26-19
    • 11.4.0+dfsg2+~cs35.7.26-20
    • 11.4.0+dfsg2+~cs35.7.26-21
    • 11.4.0+dfsg2+~cs35.7.26-7
    • 11.4.0+dfsg2+~cs35.7.26-8
    • 11.4.0+dfsg2+~cs35.7.26-9
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

  • node-webfont Debian:13

    Versions
    • 11.4.0+dfsg2+~cs35.7.26-13
    • 11.4.0+dfsg2+~cs35.7.26-14
    • 11.4.0+dfsg2+~cs35.7.26-15
    • 11.4.0+dfsg2+~cs35.7.26-16
    • 11.4.0+dfsg2+~cs35.7.26-18
    • 11.4.0+dfsg2+~cs35.7.26-19
    • 11.4.0+dfsg2+~cs35.7.26-20
    • 11.4.0+dfsg2+~cs35.7.26-21
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

  • node-webfont Debian:14

    Versions
    • 11.4.0+dfsg2+~cs35.7.26-13
    • 11.4.0+dfsg2+~cs35.7.26-14
    • 11.4.0+dfsg2+~cs35.7.26-15
    • 11.4.0+dfsg2+~cs35.7.26-16
    • 11.4.0+dfsg2+~cs35.7.26-18
    • 11.4.0+dfsg2+~cs35.7.26-19
    • 11.4.0+dfsg2+~cs35.7.26-20
    • 11.4.0+dfsg2+~cs35.7.26-21
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

  • fast-xml-parser npm

    Affected ranges
    • SEMVER: ≥ 4.0.0-beta.3, < 4.5.5

    Update to 4.5.5

  • fast-xml-parser npm

    Affected ranges
    • SEMVER: ≥ 5.0.0, < 5.5.7

    Update to 5.5.7

  • node-webfont Ubuntu:24.04:LTS

    Versions
    • 11.4.0+dfsg2+~cs35.7.26-7ubuntu1
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

  • node-webfont Ubuntu:25.10

    Versions
    • 11.4.0+dfsg2+~cs35.7.26-10
    • 11.4.0+dfsg2+~cs35.7.26-13ubuntu2
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

  • node-webfont Ubuntu:26.10

    Versions
    • 11.4.0+dfsg2+~cs35.7.26-18
    • 11.4.0+dfsg2+~cs35.7.26-19
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

  • node-webfont Ubuntu:26.04:LTS

    Versions
    • 11.4.0+dfsg2+~cs35.7.26-13ubuntu2
    • 11.4.0+dfsg2+~cs35.7.26-14
    • 11.4.0+dfsg2+~cs35.7.26-15
    • 11.4.0+dfsg2+~cs35.7.26-16build1
    • 11.4.0+dfsg2+~cs35.7.26-18
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

Original sources

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