NaturalIntelligence fast-xml-parser up to 5.11.x XML Parser OrderedObjParser.js readStopNodeData resource consumption

Summaryinfo

A vulnerability was found in NaturalIntelligence fast-xml-parser up to 5.11.x. It has been classified as problematic. Affected is the function readStopNodeData of the file OrderedObjParser.js of the component XML Parser. This manipulation causes resource consumption. The identification of this vulnerability is CVE-2026-126066. It is possible to initiate the attack remotely. There is no exploit available. Upgrading the affected component is recommended.

Detailsinfo

A vulnerability classified as problematic was found in NaturalIntelligence fast-xml-parser up to 5.11.x. Affected by this vulnerability is the function readStopNodeData of the file OrderedObjParser.js of the component XML Parser. The manipulation with an unknown input leads to a resource consumption vulnerability. The CWE definition for the vulnerability is CWE-400. The product does not properly control the allocation and maintenance of a limited resource. As an impact it is known to affect availability. The summary by CVE is:

fast-xml-parser allows users to process XML from JS object without C/C++ based libraries or callbacks. Prior to 5.12.0, when the non-default stopNodes option is enabled, readStopNodeData() in OrderedObjParser.js calls readTagExp() for each less-than character in an unterminated stop-node body and repeatedly rescans the remaining input while looking for a closing greater-than character. An attacker who supplies XML containing many tag fragments without a later closing character can cause quadratic rescanning before parsing fails, blocking a Node.js event loop and causing CPU-exhaustion denial of service. This issue is fixed in version 5.12.0.

It is possible to read the advisory at github.com. This vulnerability is known as CVE-2026-126066 since 11/10/2026. The exploitation appears to be easy. The attack can be launched remotely. The exploitation doesn't need any form of authentication. Technical details of the vulnerability are known, but there is no available exploit. The attack technique deployed by this issue is T1499 according to MITRE ATT&CK.

Upgrading to version 5.12.0 eliminates this vulnerability.

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Productinfo

Vendor

• NaturalIntelligence

Name

• fast-xml-parser

Version

• 5.0
• 5.1
• 5.2
• 5.3
• 5.4
• 5.5
• 5.6
• 5.7
• 5.8
• 5.9
• 5.10
• 5.11

Website

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

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