5.9

CVE-2026-33349

Exploit

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

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.
Daten sind bereitgestellt durch National Vulnerability Database (NVD)
Naturalintelligence ≫ Fast-xml-parser Version >= 4.0.1 < 4.5.5
Naturalintelligence ≫ Fast-xml-parser Version >= 5.0.0 < 5.5.7
Naturalintelligence ≫ Fast-xml-parser Version4.0.0 Update-
Naturalintelligence ≫ Fast-xml-parser Version4.0.0 Updatebeta3
Naturalintelligence ≫ Fast-xml-parser Version4.0.0 Updatebeta4
Naturalintelligence ≫ Fast-xml-parser Version4.0.0 Updatebeta5
Naturalintelligence ≫ Fast-xml-parser Version4.0.0 Updatebeta6
Naturalintelligence ≫ Fast-xml-parser Version4.0.0 Updatebeta7
Naturalintelligence ≫ Fast-xml-parser Version4.0.0 Updatebeta8
VulnDex Vulnerability Enrichment
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Zu dieser CVE wurde keine Warnung gefunden.
EPSS Metriken
Typ Quelle Score Percentile
EPSS FIRST.org 0.45% 0.356
CVSS Metriken
Quelle Base Score Exploit Score Impact Score Vector String
security-advisories@github.com 5.9 2.2 3.6
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
CWE-1284 Improper Validation of Specified Quantity in Input

The product receives input that is expected to specify a quantity (such as size or length), but it does not validate or incorrectly validates that the quantity has the required properties.

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