📄 Description (English)
Base64 Decoder 1.1.2 contains a stack-based buffer overflow vulnerability that allows local attackers to execute arbitrary code by triggering a structured exception handler (SEH) overwrite. Attackers can craft a malicious input file that overflows a buffer, overwrites the SEH chain with a POP-POP-RET gadget address, and uses an egghunter payload to locate and execute shellcode for code execution.
🤖 AI Executive Summary
CVE-2019-25634 is a stack-based buffer overflow vulnerability in Base64 Decoder 1.1.2 that allows local attackers to execute arbitrary code through SEH chain manipulation. With a CVSS score of 8.4, this vulnerability poses a significant risk to organizations using this utility for data processing. No patch is currently available, requiring immediate compensating controls and alternative solutions.
📄 Description (Arabic)
🤖 AI Intelligence Analysis Analyzed: Apr 24, 2026 11:51
🇸🇦 Saudi Arabia Impact Assessment
This vulnerability primarily affects Saudi government agencies, financial institutions, and healthcare organizations that may use Base64 Decoder 1.1.2 for data encoding/decoding operations. Banking sector (SAMA-regulated entities) and government ministries (NCA oversight) face elevated risk if this utility is deployed in legacy systems or administrative tools. Telecommunications operators and energy sector organizations using this decoder in data processing pipelines are also at risk. The local attack vector limits exposure but poses significant insider threat risk in multi-user environments common in Saudi enterprises.
🏢 Affected Saudi Sectors
Government (NCA-regulated agencies)
Banking and Financial Services (SAMA-regulated)
Healthcare
Energy and Utilities (ARAMCO, related entities)
Telecommunications (STC, Mobily, Zain)
Education
Critical Infrastructure
🎯 MITRE ATT&CK Techniques
⚖️ Saudi Risk Score (AI)
7.2
/ 10.0
🔧 Remediation Steps (English)
Immediate Actions:
1. Inventory all systems running Base64 Decoder 1.1.2 across your organization
2. Restrict local access to systems running this utility using principle of least privilege
3. Implement application whitelisting to prevent unauthorized execution
4. Monitor for suspicious process creation and SEH chain modifications
Compensating Controls (No Patch Available):
1. Migrate to alternative Base64 decoding solutions (e.g., built-in OS utilities, OpenSSL, or reputable libraries)
2. Implement Data Execution Prevention (DEP) and Address Space Layout Randomization (ASLR) at OS level
3. Deploy host-based intrusion detection systems (HIDS) to monitor buffer overflow attempts
4. Restrict file upload/input sources to trusted channels only
5. Run the utility in isolated/sandboxed environments if migration is not immediately possible
Detection Rules:
1. Monitor for Base64Decoder.exe process creation with suspicious parent processes
2. Alert on SEH chain modifications or structured exception handler overwrites
3. Detect unusual memory access patterns or egghunter shellcode signatures
4. Flag processes attempting to write to stack memory regions
5. Monitor for POP-POP-RET gadget address references in memory
🔧 خطوات المعالجة (العربية)
الإجراءات الفورية:
1. قم بحصر جميع الأنظمة التي تقوم بتشغيل Base64 Decoder 1.1.2 عبر مؤسستك
2. قيد الوصول المحلي للأنظمة التي تقوم بتشغيل هذه الأداة باستخدام مبدأ أقل صلاحية
3. طبق قائمة التطبيقات المسموحة لمنع التنفيذ غير المصرح به
4. راقب إنشاء العمليات المريبة وتعديلات سلسلة معالج الاستثناءات
الضوابط التعويضية (لا يتوفر تصحيح):
1. انتقل إلى حلول فك تشفير Base64 بديلة (مثل أدوات نظام التشغيل المدمجة أو OpenSSL أو المكتبات الموثوقة)
2. طبق منع تنفيذ البيانات (DEP) وعشوائية تخطيط مساحة العناوين (ASLR) على مستوى نظام التشغيل
3. نشر أنظمة الكشف عن الاختراقات المستندة إلى المضيف (HIDS) لمراقبة محاولات تجاوز المخزن المؤقت
4. قيد مصادر تحميل الملفات/الإدخال على القنوات الموثوقة فقط
5. قم بتشغيل الأداة في بيئات معزولة/محصورة إذا لم يكن الترحيل ممكناً على الفور
قواعد الكشف:
1. راقب إنشاء عملية Base64Decoder.exe مع عمليات أب مريبة
2. تنبيه على تعديلات سلسلة معالج الاستثناءات أو الكتابة فوق معالج الاستثناءات المنظمة
3. كشف أنماط الوصول إلى الذاكرة غير العادية أو توقيعات حمولة egghunter
4. علم العمليات التي تحاول الكتابة إلى مناطق ذاكرة المكدس
5. راقب مراجع عنوان gadget POP-POP-RET في الذاكرة
📋 Regulatory Compliance Mapping
🟢 NCA ECC 2024
A.5.1.1 - Information Security Policies (vulnerability management)
A.8.1.1 - User Access Management (least privilege enforcement)
A.12.2.1 - Change Management (patch/remediation procedures)
A.12.6.1 - Management of Technical Vulnerabilities (vulnerability assessment)
🔵 SAMA CSF
ID.RA-1 - Asset Management (inventory of vulnerable systems)
PR.AC-1 - Access Control (restrict local access)
PR.PT-1 - Protection Technology (DEP/ASLR implementation)
DE.CM-1 - Detection and Analysis (monitoring for exploitation)
🟡 ISO 27001:2022
A.12.6.1 - Management of technical vulnerabilities
A.14.2.1 - Secure development policy
A.12.2.1 - Change management procedures
A.5.1.1 - Information security policies and procedures
🟣 PCI DSS v4.0.1
6.2 - Ensure security patches are installed
11.2 - Run automated vulnerability scans
2.2.4 - Configure system security parameters
🔗 References & Sources 4
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http://4mhz.de/b64dec.html
disclosure@vulncheck.com
http://4mhz.de/download.php?file=b64dec-1-1-2.zip
disclosure@vulncheck.com
https://www.exploit-db.com/exploits/46625
disclosure@vulncheck.com
https://www.vulncheck.com/advisories/base64-decoder-local-buffer-overflow-seh-egghunter
disclosure@vulncheck.com