CVE-2026-27942

fast-xml-parser has stack overflow in XMLBuilder with preserveOrder

HIGH
7.5
CVSS Score
Published: February 26, 2026 at 01:22 AM UTC
Updated: June 17, 2026 at 10:27 AM UTC
1 product affected across 1 vendorFast XML Parser

Using fast-xml-parser by NaturalIntelligence?

Get instant alerts when new vulnerabilities affect fast-xml-parser - before attackers find them.

Real-time alertsTrack your software stackFree plan available
Severity
HIGH7.5
Exploit prediction
EPSS 0.5%
SSVC
No known exploit

Description

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.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

v < 4.5.4v < 5.3.85.0.0 ≤ v < 5.3.8
Affected range stops below 5.3.8, so it looks safe — our inference, not a vendor statement

SSVC — Action Prioritization

SSVCNo known exploitNot automatablePartial impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

Attack Vector
NETWORK
Complexity
LOW
Privileges
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality
NONE
Integrity
NONE
Availability
HIGH
Vector?

Quick Info

StatusANALYZED
CWE
CWE-120

Get alerted

Stop reading CVE feeds looking for your own stack

Track the products you run and VulnTracker tells you when a new CVE affects them — with what is known about fixing it, and nothing about the rest.

Free plan, no card