Exploit:Java/CVE-2013-2423

Threat in context

Java is a general-purpose programming language, but cases of this exploit are targeted against the Java plug-in for web browsers. The intent of the Java plug-in is that Java programs (or "applets") can be offered by websites, and run in a "sandbox" where the Java plug-in enforces rules on what the Java applet can do so that it cannot escape restricted environment.

What is an exploit?

Exploits are written to take advantage of weaknesses (or vulnerabilities) in legitimate software. A project called Common Vulnerabilities and Exposures (CVE) gives each vulnerability a unique number, in this case "CVE-2013-2423". The portion "2013" refers to the year the vulnerability was discovered, and "2423" is a unique ID for this specific vulnerability. You can find more information on the CVE website.

Payload

Downloads and installs files

If you visit a website containing the malicious code while using a vulnerable version of Java, Exploit:Java/CVE-2013-2423 is loaded. It then tries to download and run files from a remote host/URL. The files that are downloaded and run could include other malware.

Additional technical details

This exploit works by causing an exploit called "type confusion" in the Java component "MethodHandles", where the Java interpreter will write 8 bytes into a 4 byte variable, thus overflowing the data into adjacent memory, (somewhat like a buffer overflow), and overriding a security check.

Attacking the security model means that the exploit might be effective on any platform the Java interpreter is on; for example Windows, MacOS, Linux, etc.

Usually the exploits are written using a few Java classes working together. The various class files are bundled into an archive called a JAR, which uses the ZIP file format. Every JAR contains a Manifest.MF file to identify itself to the Java Runtime. Since it is found in every JAR, it won't be listed.

Below are some examples of the JAR files that exploit the vulnerability described in CVE-2013-2423:

• 061be17741f0918bbf458812f6a04ebf3b70dea5
• Astra.class
• GGG1.class
• GGG4.class
• Gomenoz.class
• Lodka1.class
• Lodka2.class
• Siura.class
• Sloza.class
• V5.class
• V7.class
• XXX2.class
• XXX3.class
• XXX8.class
• ZZ61.class
• ZZ6Z.class
• 28dc42c7b66a6a9e45d07397f1be684e1acb1372
• Auto.class
• Bommon.class
• Doner.class
• Geme.class
• GrabmGold.class
• Hoper.class
• J3.class
• MMM2.class
• Rumine.class
• Semen.class
• Soliter.class
• Tamana.class
• Truten.class
• Uglerod.class
• 3866d78f233e5458c3244043b43006e9b3213582
• Auto.class
• Barmendsha.class
• Doperz.class
• GotikaRot.class
• Jan.class
• Mzama.class
• Rollkatak.class
• Smortan1.class
• Svergo2.class
• Svilis.class
• Symerki.class
• Tronzone.class
• Ulikidema.class
• 5b90f226256b2853e38ffab6f3b1cb651b9f90b2
• ActiveX.class
• C1.class
• C2.class
• Exploit.class
• SystemClass.class
• SystemClassBase.class
• Union1.class
• Union2.class
• Z1.class
• 5e0ad173659e9e2e06d89ffa3e98738a6ddecdac
• Auto.class
• Bommon.class
• Doner.class
• Geme.class
• GeraDold.class
• Humonad.class
• kis.av
• MMM2.class
• MMM3.class
• Rumine.class
• Samurain.class
• Slemge.class
• Temerlan.class
• Truten.class
• Ulitka.class
• 6c388af46e222a264344c67168d21569cf6e088c
• Archive.class
• Chrdak.class
• Cont.class
• Egnxuir.class
• Fuj.class
• Igid.class
• Ivuy.class
• Kiparic.class
• Klpmm.class
• Luka.class
• Nakei.class
• Rom.class
• Tepvi.class
• 8619454ec435a727f52ca795c2b1316420e82c4e
• FieldAdd.class
• FieldMn22.class
• ImageAdd.class
• ImagManM2C2S2.class
• ImagManM2y2B2i2g2I2n2t2.class
• ImagManML.class
• ImagMan.class
• Inner.class
• Main.class23
• MainestAddi.class
• MainestAddi2.class
• SysoClass.class
• Union11111111.class
• Union22222222.class

Once the exploit obtains full privileges on your PC, it may:

• Run an executable file (that might be malware) included in the JAR
• Run an executable file (that might be malware) from a URL hard-coded in the exploit's file
• Take instructions from the HTML file (like a URL to the malware executable) that loaded them

Related information / Related references

You can read more about this exploit in the following articles:

• Java is So Confusing...
• Vulnerability Summary for CVE-2013-2423

Analysis by Chris Stubbs