NaturalIntelligence fast-xml-parser up to 5.3.3 denial of service

Summaryinfo

A vulnerability was found in NaturalIntelligence fast-xml-parser up to 5.3.3 and classified as problematic. Affected by this vulnerability is an unknown functionality. Such manipulation leads to denial of service. This vulnerability is listed as CVE-2026-25128. The attack may be performed from remote. There is no available exploit. It is suggested to upgrade the affected component.

Detailsinfo

A vulnerability was found in NaturalIntelligence fast-xml-parser up to 5.3.3 and classified as problematic. Affected by this issue is an unknown code. The manipulation with an unknown input leads to a denial of service vulnerability. Using CWE to declare the problem leads to CWE-404. The product does not release or incorrectly releases a resource before it is made available for re-use. Impacted is availability. CVE summarizes:

fast-xml-parser allows users to validate XML, parse XML to JS object, or build XML from JS object without C/C++ based libraries and no callback. In versions 5.0.9 through 5.3.3, a RangeError vulnerability exists in the numeric entity processing of fast-xml-parser when parsing XML with out-of-range entity code points (e.g., `�` or `�`). This causes the parser to throw an uncaught exception, crashing any application that processes untrusted XML input. Version 5.3.4 fixes the issue.

The advisory is shared for download at github.com. This vulnerability is handled as CVE-2026-25128 since 01/29/2026. The exploitation is known to be easy. The attack may be launched remotely. No form of authentication is required for exploitation. There are neither technical details nor an exploit publicly available. The MITRE ATT&CK project declares the attack technique as T1499.

The vulnerability scanner Nessus provides a plugin with the ID 297652 (Linux Distros Unpatched Vulnerability : CVE-2026-25128), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 5.3.4 eliminates this vulnerability.

The vulnerability is also documented in the databases at Tenable (297652) and CERT Bund (WID-SEC-2026-0526). Once again VulDB remains the best source for vulnerability data.

Affected

• IBM App Connect Enterprise

Productinfo

Vendor

• NaturalIntelligence

Name

• fast-xml-parser

Version

• 5.3.0
• 5.3.1
• 5.3.2
• 5.3.3

Website

• Product: https://github.com/NaturalIntelligence/fast-xml-parser/

CPE 2.3info

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Once again VulDB remains the best source for vulnerability data.

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