Exploit:Java/CVE-2011-3544

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 outside the webpage it is included in.

What is an exploit?

Exploits are written to take advantage of weaknesses (or "vulnerabilities") in legitimate software. A project called "Common Vulnerabilities and Exposures" (or "CVE"), used by many vendors and organizations, gives each vulnerability a unique number, in this case "CVE-2011-3544". The portion "2011" refers to the year the vulnerability was discovered, and "3544" is a unique ID for this specific vulnerability. The official source that gives out CVE identifiers lists this at http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2011-3544.

Payload

Downloads and installs files

If you visit a website containing the malicious code while using a vulnerable version of Java, Exploit:Java/CVE-2011-3544 is loaded. It then tries to download and run files from a remote host/URL. The files that are downloaded and run could be any of the hacker's choice and could include additional malware.

Additional technical details

Exploit:Java/CVE-2011-3544 uses a bug in the JavaScript engine inside of the Java Runtime. Java applets can run JavaScript code, and normally the JavaScript code is subject to the same restrictions that the Java applet is. The JavaScript function in this exploit extends the internal function "toString" with its own code. Then it calls a built-in, privileged routine, like the Error object, that it knows will call the "toString" function that it just redefined. When it calls the "toString" function, the attacker’s code is then run with elevated privileges. The exploit takes these privileges and can then run outside of the sandbox.

In summary, Exploit:Java/CVE-2011-3544 attacks the security model instead of a buffer overflow. With a buffer overflow, the exploit is dependent on the specific CPU (Central Processing Unit), and might be affected by technology like DEP (Data Execution Prevention) or ASLR (Address Space Layout Randomization).

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 files that exploit the vulnerability described in CVE-2011-3544:

• 00090b78cd0730dd0f4d04be9ff213b35545c1da
• abcred.class
• i.class
• 00237384c62d1e260f6ed9a277f80bdd37cc3a61, 029bb2d8f3bc7cf79cd249798b69d3410efee6a0, 033d594bcaa585db419f76aeaca0edd74c8e02aa
• Final.class
• j.class
• n.class
• 002fcef6e70c9227420a2e97bafa038c9f14cc0d
• file.bin - detected as TrojanDownloader:Win32/Sonide.A
• yokai.class
• 00c12fd7e080575de56869f66e4d8a973ca96f74, 023683cb65ff1a7779d0d66427fa8ce5f21d65c4, 026298551b026211c2533274c02f060438eb6107
• Final.class
• q.class
• 019b19718b76238322efde40f198c95beab11b8d
• Final.class
• v.class
• 01bd5a820497cd98b33b3548feb465be8f6c3ad1
• ScriptEngineExp.class
• 01e5873ebdc406428c0417f566c71b5dfe99e814
• notana.class
• 0203f381dda60ad68b0dd9eba9e4b83dfa88a13d
• Applet.class
• d.class
• 02da44e5f7f4817697162cf7da2c7e9445ceb1d6
• Applet.class
• 033b8a2d9b8c6cf0acd4d9707cdc7c853e9c3e45
• Final.class
• m.class
• q.class
• 0368f2cbb64102d2923468e736f1c624abb1aa03
• trinity.class

Some payloads are specifically targeted against MacOS X, for example:

• 7cdc96c8705aeb324aa08b9cc3c171b9da67f576
• Exploit.class
• metasploit.dat (a configuration file for the payload)
• Payload.class

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

• Run a file (that may be detected as malware) included in the JAR
• Run a file from (that may be detected as malware) a URL hardcoded in the exploit's file
• Take instructions from the HTML file (like a URL to the malware file) that loaded them

In the wild, we have observed the following malware being distributed in the exploit's JAR files:

• Backdoor:Win32/Poison.BO
• Backdoor:Win32/Poison.E
• PWS:Win32/OnLineGames.LL
• PWS:Win32/Wowsteal.BC
• TrojanDownloader:Win32/Sonide.A
• TrojanDropper:Win32/Machime.B

Related information / Related references

The articles referenced below outline some of the the technical details of the weakness this vulnerability exploits:

• http://schierlm.users.sourceforge.net/CVE-2011-3544.html
• http://labs.m86security.com/tag/cve-2011-3544/

Analysis by Chris Stubbs