TippingPoint Zero Day Initiative

Apple Webkit Font Glyph Layout Remote Code Execution Vulnerability

ZDI-11-099: March 2nd, 2011


CVSS Score

Affected Vendors

Affected Products

TippingPoint™ IPS Customer Protection

TippingPoint IPS customers are protected against this vulnerability by Digital Vaccine protection filter ID 10870. For further product information on the TippingPoint IPS:

Vulnerability Details

This vulnerability allows remote attackers to execute arbitrary code on vulnerable installations of Apple Safari's Webkit. User interaction is required to exploit this vulnerability in that the target must visit a malicious page or open a malicious file.

The specific flaw exists within the way the application handles floating blocks in certain situations. When performing layout operations for a floating block produced by a pseudo-element, the application will attempt to access glyph data that hasn't been fully assigned into the glyph data hashmap. Due to this type being incomplete, this can lead to code execution under the context of the application.

Vendor Response

Apple has issued an update to correct this vulnerability. More details can be found at:

Disclosure Timeline

    2010-10-18 - Vulnerability reported to vendor
    2011-03-02 - Coordinated public release of advisory


This vulnerability was discovered by:
    wushi of team509