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CVE-2026-33349 - Vulnerability Analysis

MediumCVSS: 5.9

Last Updated: March 26, 2026

fast-xml-parser - Denial of Service

Published: March 24, 2026Updated: March 26, 2026PoC AvailableRemote Exploitable

Overview

fast-xml-parser >= 4.0.0-beta.3 and < 5.5.7 contains a denial of service caused by improper JavaScript truthy checks in DocTypeReader for maxEntityCount and maxEntitySize, letting attackers trigger unbounded entity expansion, exploit requires attacker to supply crafted XML input.

Severity & Score

Severity: Medium

CVSS Score: 5.9

Impact

Attackers can cause memory exhaustion and denial of service by triggering unbounded entity expansion.

Mitigation

Upgrade to version 5.5.7 or later.

References

https://github.com/NaturalIntelligence/fast-xml-parser/commit/239b64aa1fc5c5455ddebbbb54a187eb68c9fdb7
https://github.com/NaturalIntelligence/fast-xml-parser/security/advisories/GHSA-jp2q-39xq-3w4g

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Details

CVE ID: CVE-2026-33349
Severity: Medium
CVSS Score: 5.9
Type: xml_external_entity_injection
Status: confirmed

CWE

CWE-1284

CVSS Metrics

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H