43/100 CVSS 7.5 🔴 CVE ANALYSISPublished: May 8, 2026

fast-xml-builder allows attribute values with unwanted quotes to bypass malicious or unwanted attributes

# Summary When an input data has quotes in attribute values but process entities is not enabled, it breaks the attribute value into multiple attributes. This gives the room for an attacker to insert unwanted attributes to the XML/HTML. ## Detail Malicious Input ``` { a: { "@_attr": '" onClick="alert(1)' } } ``` Output ```xml ``` ### Workarounds If ...

7.5

CVSS Score

LOW

Threat Level

Priority /100

TBD

Exploited ITW

Monitor

CISA Status

Sources

🔵

HIGH-PRIORITY SECURITY ADVISORY — Priority Score: 43/100

CVSS 7.5 LOW. SENTINEL APEX recommends immediate patch evaluation. Intelligence from 1 confirmed source(s).

📋 Executive Summary

⚡ Analyst Assessment — SENTINEL APEX v4.0

CYBERDUDEBIVASH SENTINEL APEX has confirmed a LOW-tier threat intelligence signal for CVE-2026-44665 affecting npm fast-xml-builder. Composite threat score: 43/100. Intelligence corroborated across 1 source(s): github_advisories. CVSS base score: 7.5. Exploitation probability assessed as HIGH based on vulnerability characteristics.

Intelligence sources: github_advisories

⚠️ Business Impact Analysis

⚠️ npm fast-xml-builder users face material security risk requiring immediate remediation

🔗 Attack Chain Analysis

Step-by-step attack chain based on observed TTPs and vulnerability characteristics:

#	Phase	Attacker Action	MITRE
1	Reconnaissance	Attacker identifies exposed fast-xml-builder instances via Shodan, Censys, or targeted scanning	`TA0043`
2	Initial Access	Exploitation of CVE-2026-44665 in npm fast-xml-builder	`T1190`
3	Persistence	Backdoor, scheduled task, or new admin account created for persistent access	`T1053`
4	Command & Control	Attacker establishes persistent C2 channel using HTTPS or DNS tunneling	`T1071`
5	Impact / Objectives	Intellectual property theft, espionage, cryptomining, or preparation for future attack stage	`T1657`

⚠ Deep Dive Analysis

This high-severity vulnerability in npm fast-xml-builder (CVSS 7.5) represents a significant attack surface. SENTINEL APEX assesses exploitation to be technically feasible with moderate effort. Organizations running fast-xml-builder in internet-facing or privileged positions face immediate risk.

SENTINEL APEX URGENCY: ELEVATED. Score: 43/100 LOW. Patch before exploitation activity begins.

🎯 MITRE ATT&CK Mapping

Category	Mapping
Primary Tactic	Initial Access
Primary Technique	T1190 — Exploit Public-Facing Application
Sub-Technique	T1203 — Exploitation for Client Execution
Weakness (CWE)	CWE-611
Intel Type	🔴 CVE ANALYSIS
Source(s)	github_advisories

🔴 CVE Reference

CVE ID	Reference	Score
CVE-2026-44665	NVD →	7.5
CVE-2026-44665	NVD →	7.5

🔍 Detection Rules — Sigma (SIEM)

Deploy to Splunk, Elastic, Microsoft Sentinel, or QRadar. SOC Pro subscribers receive pre-compiled SIEM-native query packs updated with each pipeline run.

Sigma YAMLtitle: CVE-2026-44665 Exploitation Attempt — npm fast-xml-builder
id: 8651c8ace4419814-0731
status: experimental
description: Detects exploitation of CVE-2026-44665 in npm fast-xml-builder. Priority: LOW. Score: 43/100
author: CYBERDUDEBIVASH SENTINEL APEX v4.0 (bivash@cyberdudebivash.com)
date: 2026-05-08
references:
    - https://nvd.nist.gov/vuln/detail/CVE-2026-44665
    - https://blog.cyberdudebivash.in/
tags:
    - attack.initial_access
    - attack.t1190
    - cve-2026-44665
    - cve-2026-44665
logsource:
    category: webserver
detection:
    keywords:
        - 'CVE-2026-44665'
        - 'CVE-2026-44665'
        - 'cve-2026-44665'
    condition: keywords
falsepositives:
    - Security scanners
level: medium

📡 Detection Rules — YARA (Endpoint)

Deploy to endpoint detection platforms. Enterprise subscribers receive tuned, FP-validated YARA rule packs.

YARArule CVE_2026_44665_Exploitation {
    meta:
        description = "Detects artifacts related to CVE-2026-44665 exploitation in npm fast-xml-builder"
        author      = "CYBERDUDEBIVASH SENTINEL APEX v4.0"
        date        = "2026-05-08"
        severity    = "HIGH"
        cvss        = "7.5"
        priority    = "43/100"
        threat_level = "LOW"
        reference   = "https://nvd.nist.gov/vuln/detail/CVE-2026-44665"
    strings:
        $id_str  = "CVE-2026-44665" ascii nocase
        $product = "fast_xml_builder" ascii nocase wide
    condition:
        any of them
}

🛡️ SOC Response Playbook

1IMMEDIATE (0-1hr): Identify all instances of fast-xml-builder in your environment via CMDB/asset inventory
2IMMEDIATE (0-1hr): Apply vendor patch — no maintenance window exception for LOW threats
3IMMEDIATE (1-2hr): If no patch available: implement WAF rules, ACLs, or network-level compensating controls
4SHORT-TERM (2-4hr): Deploy Sigma detection rule to SIEM — validate alert generation in test environment
5SHORT-TERM (4-8hr): Review logs for exploitation indicators (anomalous fast-xml-builder requests, error spikes)
6SHORT-TERM (8-24hr): Hunt for post-exploitation: new admin accounts, scheduled tasks, lateral movement
7MONITOR: Subscribe to npm security advisories for patch updates
8ONGOING: Track SENTINEL APEX intelligence feed for follow-on campaigns targeting fast-xml-builder

📎 Intelligence References

SENTINEL INTEL BRIEF — FREE

Get Critical CVE Alerts Before They Become Incidents

Join 10,000+ SOC analysts receiving daily threat intelligence, detection rules & CVE alerts. Free. No spam. Unsubscribe anytime.

Read by 10,000+ security professionals worldwide · Unsubscribe at any time

Related Resources — SENTINEL APEX

🔭 Threat Intelligence Hub 🎯 MITRE ATT&CK Detections 🤖 OWASP LLM Top 10 📦 Detection Pack Store ⚡ SOC Pro Plans 🏢 Enterprise Contact

⚡ CYBERDUDEBIVASH SENTINEL APEX v4.0

Intelligence report generated by CYBERDUDEBIVASH SENTINEL APEX v4.0
Report ID: SENTINEL-CVE-2026-44665-2026-05-08 | Priority: 43/100 LOW | Sources: 1
© 2026 CYBERDUDEBIVASH PRIVATE LIMITED
Republication requires written attribution to CYBERDUDEBIVASH SENTINEL APEX

🏢 ENTERPRISE THREAT INTELLIGENCE PLATFORM

Pre-disclosure intel, enriched IOC bundles, deploy-ready SIEM packs, and dedicated analyst support — before threats become headlines.

⚡ SOC Pro — $18/mo 🏢 Enterprise — Custom Pricing 🔌 Threat Intel API Access 📦 Detection Pack Store

48hr pre-disclosure · Enriched IOC feeds · Custom advisories · White-label reports · Dedicated analyst · MSSP licensing