📄 Description (English)
Exim Buffer Overflow Vulnerability — Exim contains a buffer overflow vulnerability in the base64d function part of the SMTP listener that may allow for remote code execution.
🤖 AI Executive Summary
CVE-2018-6789 is a critical buffer overflow vulnerability in Exim mail server's base64 decoding function (base64d) within the SMTP listener. This vulnerability allows unauthenticated remote attackers to execute arbitrary code on affected Exim mail servers by sending specially crafted base64-encoded data. With a CVSS score of 9.0 and publicly available exploits, this represents an immediate threat to any organization running unpatched Exim instances. The vulnerability affects all versions of Exim before 4.90.1 and has been actively exploited in the wild.
📄 Description (Arabic)
🤖 AI Intelligence Analysis Analyzed: Apr 11, 2026 07:05
🇸🇦 Saudi Arabia Impact Assessment
Exim is one of the most widely deployed mail transfer agents (MTAs) globally, and Saudi organizations across multiple sectors are likely affected. Government entities regulated by NCA that use Linux-based mail infrastructure are at high risk. Banking and financial institutions under SAMA regulation may have Exim instances in their email infrastructure. Saudi telecom providers (STC, Mobily, Zain) and ISPs commonly deploy Exim for mail relay services. Energy sector organizations including ARAMCO and utility companies with Linux-based mail servers are vulnerable. Educational institutions and healthcare organizations in Saudi Arabia that rely on open-source mail solutions are also at significant risk. Successful exploitation could lead to complete server compromise, data exfiltration of sensitive emails, and lateral movement within organizational networks.
🏢 Affected Saudi Sectors
Government
Banking
Telecommunications
Energy
Healthcare
Education
Defense
Retail
⚖️ Saudi Risk Score (AI)
9.2
/ 10.0
🔧 Remediation Steps (English)
IMMEDIATE ACTIONS:
1. Identify all Exim mail server instances across your infrastructure using asset discovery tools
2. Check Exim version: run 'exim --version' — any version before 4.90.1 is vulnerable
3. Apply emergency patching: upgrade Exim to version 4.90.1 or later immediately
PATCHING GUIDANCE:
1. Update Exim via package manager: 'apt-get update && apt-get install exim4' (Debian/Ubuntu) or 'yum update exim' (RHEL/CentOS)
2. If using custom-compiled Exim, download and compile version 4.90.1+ from official sources
3. Restart the Exim service after patching
4. Verify the updated version is running
COMPENSATING CONTROLS (if immediate patching is not possible):
1. Place a WAF or reverse proxy in front of SMTP services to filter malicious base64 payloads
2. Restrict SMTP access to trusted IP ranges using firewall rules
3. Implement network segmentation to isolate mail servers
4. Disable unnecessary SMTP authentication mechanisms temporarily
DETECTION RULES:
1. Monitor SMTP traffic for unusually large base64-encoded strings in SMTP commands
2. Deploy IDS/IPS signatures for CVE-2018-6789 (Snort/Suricata rules available)
3. Monitor Exim logs for crashes or unexpected behavior
4. Check for indicators of compromise: unexpected processes, new user accounts, or outbound connections from mail servers
5. Review CISA KEV catalog — this vulnerability is listed as actively exploited
🔧 خطوات المعالجة (العربية)
الإجراءات الفورية:
1. تحديد جميع خوادم Exim في البنية التحتية باستخدام أدوات اكتشاف الأصول
2. التحقق من إصدار Exim: تشغيل 'exim --version' — أي إصدار قبل 4.90.1 معرض للخطر
3. تطبيق التحديث الطارئ: ترقية Exim إلى الإصدار 4.90.1 أو أحدث فوراً
إرشادات التحديث:
1. تحديث Exim عبر مدير الحزم: 'apt-get update && apt-get install exim4' (Debian/Ubuntu) أو 'yum update exim' (RHEL/CentOS)
2. إذا كنت تستخدم Exim مُجمّع مخصص، قم بتنزيل وتجميع الإصدار 4.90.1+ من المصادر الرسمية
3. إعادة تشغيل خدمة Exim بعد التحديث
4. التحقق من تشغيل الإصدار المحدث
الضوابط التعويضية (إذا لم يكن التحديث الفوري ممكناً):
1. وضع جدار حماية تطبيقات الويب أو وكيل عكسي أمام خدمات SMTP لتصفية حمولات base64 الضارة
2. تقييد الوصول إلى SMTP على نطاقات IP الموثوقة باستخدام قواعد جدار الحماية
3. تنفيذ تجزئة الشبكة لعزل خوادم البريد
4. تعطيل آليات مصادقة SMTP غير الضرورية مؤقتاً
قواعد الكشف:
1. مراقبة حركة SMTP بحثاً عن سلاسل base64 كبيرة بشكل غير عادي في أوامر SMTP
2. نشر توقيعات IDS/IPS لـ CVE-2018-6789 (توقيعات Snort/Suricata متاحة)
3. مراقبة سجلات Exim بحثاً عن أعطال أو سلوك غير متوقع
4. التحقق من مؤشرات الاختراق: عمليات غير متوقعة أو حسابات مستخدمين جديدة أو اتصالات صادرة من خوادم البريد
📋 Regulatory Compliance Mapping
🟢 NCA ECC 2024
ECC 2-3-1 (Patch Management)
ECC 2-5-1 (Network Security)
ECC 2-3-4 (Vulnerability Management)
ECC 2-6-1 (Email Security)
ECC 2-2-1 (Asset Management)
🔵 SAMA CSF
SAMA CSF 3.3.3 (Patch Management)
SAMA CSF 3.3.5 (Vulnerability Management)
SAMA CSF 3.4.1 (Network Security Management)
SAMA CSF 3.3.7 (Secure Configuration)
SAMA CSF 3.5.1 (Incident Management)
🟡 ISO 27001:2022
A.8.8 (Management of technical vulnerabilities)
A.8.9 (Configuration management)
A.8.20 (Networks security)
A.8.23 (Web filtering)
A.5.24 (Information security incident management planning)
🟣 PCI DSS v4.0
PCI DSS 6.3.3 (Install critical security patches within one month)
PCI DSS 11.3 (Penetration testing)
PCI DSS 6.2 (Develop software securely)
PCI DSS 1.3 (Network access controls)
🔗 References & Sources 0
No references.
📦 Affected Products / CPE 1 entries
Exim:Exim