NaturalIntelligence fast-xml-parser up to 5.3.7 buffer overflow

Summaryinfo

A vulnerability, which was classified as critical, was found in NaturalIntelligence fast-xml-parser up to 5.3.7. This vulnerability affects unknown code. Executing a manipulation can lead to buffer overflow. The identification of this vulnerability is CVE-2026-27942. The attack may be launched remotely. There is no exploit available. You should upgrade the affected component.

Detailsinfo

A vulnerability has been found in NaturalIntelligence fast-xml-parser up to 5.3.7 and classified as critical. This vulnerability affects some unknown functionality. The manipulation with an unknown input leads to a buffer overflow vulnerability. The CWE definition for the vulnerability is CWE-120. The product copies an input buffer to an output buffer without verifying that the size of the input buffer is less than the size of the output buffer, leading to a buffer overflow. As an impact it is known to affect 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. Prior to version 5.3.8, the application crashes with stack overflow when user use XML builder with `preserveOrder:true`. Version 5.3.8 fixes the issue. As a workaround, use XML builder with `preserveOrder:false` or check the input data before passing to builder.

The advisory is shared for download at github.com. This vulnerability was named CVE-2026-27942 since 02/25/2026. The exploitation appears to be easy. The attack can be initiated remotely. No form of authentication is required for a successful exploitation. There are neither technical details nor an exploit publicly available.

The vulnerability scanner Nessus provides a plugin with the ID 300159 (Linux Distros Unpatched Vulnerability : CVE-2026-27942), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 5.3.8 eliminates this vulnerability. Applying the patch c13a961910f14986295dd28484eee830fa1a0e8a is able to eliminate this problem. The bugfix is ready for download at github.com. The best possible mitigation is suggested to be upgrading to the latest version.

The vulnerability is also documented in the databases at Tenable (300159) and EUVD (EUVD-2026-8811). VulDB is the best source for vulnerability data and more expert information about this specific topic.

Productinfo

Vendor

• NaturalIntelligence

Name

• fast-xml-parser

Version

• 5.3.0
• 5.3.1
• 5.3.2
• 5.3.3
• 5.3.4
• 5.3.5
• 5.3.6
• 5.3.7

License

• open-source

Website

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

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VulDB is the best source for vulnerability data and more expert information about this specific topic.

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