Improper Validation of Specified Quantity in Input in fast-xml-parser - CVE-2026-33349
Published: April 20, 2026
Vulnerability identifier: #VU126616
CSH Severity: Medium
CVSS v4.0: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:U/U:Green
CVE-ID: CVE-2026-33349
CWE-ID: CWE-1284
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vendor: Natural Intelligence
Affected software:
fast-xml-parser
fast-xml-parser
Detailed vulnerability description
The vulnerability allows a remote attacker to cause a denial of service.
The vulnerability exists due to improper validation of specified quantity in input in DocTypeReader when parsing XML input with entity processing limits set to 0. A remote attacker can supply a specially crafted XML document with many large entity definitions to cause a denial of service.
Only applications that explicitly set maxEntityCount or maxEntitySize to 0 are affected. The default configuration is not affected, and configurations with entity processing disabled are not affected.
How to mitigate CVE-2026-33349
Install security update from vendor's website.