Public Vulnerability Reports

Multiple Vendor FreeType2 PFB Integer Overflow Vulnerability

06.10.08

BACKGROUND

FreeType2 is an open source library for parsing fonts that is used by many applications. This includes projects such as X.Org, Second Life, GD2, and OpenJDK. For more information, please see the vendor's website at the following URL.

http://freetype.sourceforge.net/freetype2/

DESCRIPTION

Remote exploitation of an integer overflow vulnerability in the FreeType2 library, as included in various vendors' operating systems, could allow an attacker to execute arbitrary code with the privileges of the affected application.

The vulnerability exists within the code responsible for parsing Printer Font Binary (PFB) format font files. PFB files contain a section known as the "Private" dictionary table which is used to describe how characters are constructed. When parsing this data structure, a series of 16-bit length values are read in from the file. These values are added together and used to allocate a dynamic buffer. The addition can result in an integer overflow, which subsequently leads to a heap overflow.

ANALYSIS

Exploitation of this vulnerability results in the execution of arbitrary code with the privileges of the application using the library. Since FreeType2 is a library and not a standalone application, the exploitation vector will vary. iDefense Labs verified that local privilege escalation was possible via the X.Org Xserver.

DETECTION

iDefense has confirmed the existence of this vulnerability in FreeType2 version 2.3.5. Previous versions may also be affected.

WORKAROUND

iDefense is currently unaware of any workarounds for this issue. Changing the permissions on the freetype.so library may not always be effective since applications that run with root privileges are not restricted by file permissions.

VENDOR RESPONSE

The FreeType maintainers addressed this vulnerability with the release of version 2.3.6. For more information, refer to the release notes at the following URL.

http://sourceforge.net/project/shownotes.php?group_id=3157&release_id=605780

CVE INFORMATION

The Common Vulnerabilities and Exposures (CVE) project has assigned the name CVE-2008-1806 to this issue. This is a candidate for inclusion in the CVE list (http://cve.mitre.org/), which standardizes names for security problems.

DISCLOSURE TIMELINE

06/03/2008 Initial vendor notification
06/04/2008 Initial vendor response
06/10/2008 Coordinated public disclosure

CREDIT

This vulnerability was reported to iDefense by regenrecht.

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LEGAL NOTICES

Copyright © 2008 Verisign, Inc.

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