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CVE-2026-42897

High 🇺🇸 CISA KEV

CWE-79 — Weakness Type

                    Published: May 14, 2026                      ·  Modified: May 17, 2026                      ·  Source: NVD                

CVSS v3

8.1

🔗 NVD Official

📄 Description (English)

Improper neutralization of input during web page generation ('cross-site scripting') in Microsoft Exchange Server allows an unauthorized attacker to perform spoofing over a network.

🤖 AI Executive Summary

A cross-site scripting (XSS) vulnerability in Microsoft Exchange Server 2016 allows attackers to perform spoofing attacks through improper input neutralization during web page generation. With a CVSS score of 8.1 and no patch currently available, this vulnerability poses significant risk to organizations relying on Exchange for email infrastructure. The lack of exploit availability provides a limited window for remediation before potential weaponization.

📄 Description (Arabic)

🤖 AI Intelligence Analysis Analyzed: May 15, 2026 23:49

🇸🇦 Saudi Arabia Impact Assessment

This vulnerability directly impacts Saudi banking sector (SAMA-regulated institutions), government agencies (NCA oversight), and critical infrastructure operators. Saudi Aramco, STC, and other major enterprises using Exchange Server 2016 are at risk of email spoofing attacks that could compromise business communications, facilitate phishing campaigns, and damage organizational reputation. The vulnerability is particularly concerning for organizations handling sensitive financial and governmental communications where email authenticity is critical.

🏢 Affected Saudi Sectors

Banking and Financial Services (SAMA-regulated) Government and Public Administration (NCA oversight) Energy and Utilities (Saudi Aramco, power generation) Telecommunications (STC, Mobily, Zain) Healthcare and Pharmaceuticals Education and Research Institutions Large Enterprise Organizations

🎯 MITRE ATT&CK Techniques

T1598.003 — Phishing: Spearphishing Link (via spoofed emails) T1566.002 — Phishing: Phishing - Spearphishing Attachment T1187 — Forced Authentication (via XSS-based credential harvesting) T1539 — Data from Cloud Storage (if XSS leads to session hijacking) T1040 — Network Sniffing (potential for MITM via spoofing) T1598.001 — Phishing: Spearphishing Attachment

⚖️ Saudi Risk Score (AI)

7.8

/ 10.0

🔧 Remediation Steps (English)

IMMEDIATE ACTIONS:

1. Inventory all Exchange Server 2016 deployments across your organization, including cumulative update levels (CU1-CU16)

2. Implement network segmentation to restrict access to Exchange OWA (Outlook Web Access) interfaces

3. Enable Enhanced Filtering for Connectors to reduce spoofing risks

4. Deploy email authentication mechanisms: SPF, DKIM, and DMARC records with strict policies



COMPENSATING CONTROLS (until patch available):

5. Implement Web Application Firewall (WAF) rules to detect and block XSS payloads in Exchange traffic

6. Enable Exchange Server logging and monitor for suspicious input patterns in web requests

7. Restrict administrative access to Exchange management interfaces

8. Deploy email gateway solutions with advanced threat protection and content filtering



DETECTION RULES:

9. Monitor IIS logs for Exchange for unusual characters in query strings and POST data (script tags, event handlers)

10. Alert on failed authentication attempts followed by XSS-pattern requests

11. Track modifications to Exchange transport rules and mail flow settings



PATCHING STRATEGY:

12. Subscribe to Microsoft Security Update Guide for CVE-2026-42897 patch release

13. Prepare test environment for patch deployment immediately upon availability

14. Plan phased rollout with priority to internet-facing Exchange servers

🔧 خطوات المعالجة (العربية)

الإجراءات الفورية:

1. قم بحصر جميع نشرات Exchange Server 2016 في مؤسستك، بما في ذلك مستويات التحديث التراكمي (CU1-CU16)

2. تطبيق تقسيم الشبكة لتقييد الوصول إلى واجهات Exchange OWA

3. تفعيل التصفية المحسّنة للموصلات لتقليل مخاطر الانتحال

4. نشر آليات المصادقة: SPF و DKIM و DMARC مع سياسات صارمة

الضوابط البديلة (حتى توفر التصحيح):

5. تطبيق قواعد جدار حماية تطبيقات الويب للكشف عن حمولات XSS وحجبها

6. تفعيل تسجيل Exchange وراقب الأنماط المريبة في طلبات الويب

7. تقييد الوصول الإداري إلى واجهات إدارة Exchange

8. نشر حلول بوابة البريد الإلكتروني مع الحماية المتقدمة من التهديدات

قواعد الكشف:

9. راقب سجلات IIS لـ Exchange للأحرف غير العادية في سلاسل الاستعلام وبيانات POST

10. تنبيهات محاولات المصادقة الفاشلة متبوعة بطلبات نمط XSS

11. تتبع التعديلات على قواعد نقل Exchange وإعدادات تدفق البريد

استراتيجية التصحيح:

12. الاشتراك في دليل تحديث أمان Microsoft لإصدار تصحيح CVE-2026-42897

13. تحضير بيئة اختبار لنشر التصحيح فوراً عند توفره

14. التخطيط للنشر المرحلي مع الأولوية لخوادم Exchange المتصلة بالإنترنت

📋 Regulatory Compliance Mapping

🟢 NCA ECC 2024

ECC 2024 - 5.1.1: Information Security Policies and Procedures ECC 2024 - 5.2.1: Access Control and Authentication ECC 2024 - 5.3.1: Cryptography and Data Protection ECC 2024 - 5.4.1: Incident Management and Response

🔵 SAMA CSF

SAMA CSF - Governance: Risk Management Framework SAMA CSF - Protect: Access Control and Authentication SAMA CSF - Detect: Security Monitoring and Logging SAMA CSF - Respond: Incident Response Procedures

🟡 ISO 27001:2022

ISO 27001:2022 - A.5.15: Access Control ISO 27001:2022 - A.5.16: Cryptography ISO 27001:2022 - A.6.5: Information Security in Supplier Relationships ISO 27001:2022 - A.8.22: Monitoring Activities ISO 27001:2022 - A.8.23: Web Application Security

🟣 PCI DSS v4.0.1

PCI DSS 4.0 - Requirement 6.2: Security patches and updates PCI DSS 4.0 - Requirement 6.4.1: Web application security PCI DSS 4.0 - Requirement 11.3: Security testing

🔗 References & Sources 2

🔗

https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-42897

secure@microsoft.com

Mitigation Vendor Advisory

🔗

https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-42897

134c704f-9b21-4f2e-91b3-4a467353bcc0

US Government Resource

📦 Affected Products / CPE 40 entries

microsoft:exchange_server:-

microsoft:exchange_server:2016

microsoft:exchange_server:2019

📊 CVSS Score

8.1

/ 10.0 — High

📊 CVSS Vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N

Attack VectorN — None / Network

Attack ComplexityL — Low / Local

Privileges RequiredN — None / Network

User InteractionR — Required

ScopeU — Unchanged

ConfidentialityH — High

IntegrityH — High

AvailabilityN — None / Network

📋 Quick Facts

Severity High

CVSS Score8.1

CWECWE-79

EPSS6.29%

Exploit No

Patch ✗ No

CISA KEV🇺🇸 Yes

Published 2026-05-14

Source Feed nvd

🇸🇦 Saudi Risk Score

7.8

/ 10.0 — Saudi Risk

Priority: HIGH

🏷️ Tags

CWE-79

🏢 Vendor Advisories

🔗 https://msrc.microsoft.com/update-guide/vulnerabilit...

⚡ Actions

🔗 NVD Official Page ⚡ Exploit-DB Search 🐙 GitHub PoC Search 🎯 MITRE ATT&CK 📊 CVE Details

CVE-2026-42897

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