The Sun Java JRE is Sun's implementation of the Java runtime. For more information, see the vendor's site found at the following link.
Remote exploitation of an integer signedness vulnerability in Sun Microsystems Inc.'s Java JRE could allow an attacker to execute arbitrary code with the privileges of the current user.
The vulnerability exists within the font parsing code in the JRE. As part of its font API, the JRE provides the ability to load a font from a remote URL.
The vulnerability occurs when parsing glyph description instructions in the font file. When parsing the glyph descriptions, a 16bit signed counter is used as the index to store the next glyph point value. This counter is compared to a 32bit value that represents the maximum size of the heap buffer. Under certain conditions, the 16bit counter will be interpreted as a negative value, which allows the attacker to store data before the allocated buffer.
Exploitation allows attackers to execute arbitrary code in the context of the currently logged-on user. To exploit this vulnerability, a targeted user must load a malicious Web page created by an attacker. An attacker typically accomplishes this via social engineering or injecting content into compromised, trusted sites.
iDefense has confirmed the existence of this vulnerability in Sun Microsystem Inc.'s Java JRE version 1.6.0_11 for Windows. Previous versions and versions for other platforms may also be affected.
Sun Microsystems reports that the vulnerability can occur in the following Java SE and Java SE for Business releases for Windows, Solaris, and Linux:
* JDK and JRE 6 Update 12 and earlier * JDK and JRE 5.0 Update 17 and earlier
There is a potential workaround for the vulnerability, but it renders the JRE unusable. It is possible to use the cacls program to change the file permissions on fontmanager.dll. This will prevent the vulnerable library from loading. This workaround can be applied with the following command line:
echo y| cacls "C:Program FilesJava**JRE_VERSION**binfontmanager.dll" /E /P everyone:N
However, this workaround has a serious impact on the functionality of the JRE. When a webpage attempts to load an applet, the JRE will abort with a runtime error, and the browser will close.
Sun Microsystem Inc. has released a patch which addresses this issue. For more information, consult their advisory at the following URL:
A Mitre Corp. Common Vulnerabilities and Exposures (CVE) number has not been assigned yet.
02/18/2009 - Initial Contact
02/18/2009 - PoC Requested
02/19/2009 - PoC Sent
03/10/2009 - Disclosure Date Set
03/25/2009 - Coordinated Public Disclosure
This vulnerability was discovered by Sean Larsson, iDefense.
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