Microsoft Internet Explorer PNG Deflate Heap Corruption Vulnerability



Date Discovered

December 12, 2002


A heap corruption vulnerability has been reported for Microsoft Internet Explorer. The vulnerability is related to the way that Microsoft Internet Explorer interprets PNG image data. The function that handles the deflation of PNG images does not properly handle some invalid data within PNG image files. An attacker can exploit this vulnerability by tricking a user into viewing a maliciously constructed PNG image file. When the image file is rendered it will trigger the heap corruption condition and overwrite critical areas in memory. Any malicious attacker-supplied code will be executed with elevated privileges. It should be noted that applications which depend on MSIE to render PNG files are also affected.

Technologies Affected

  • Microsoft Internet Explorer 5.0.1
  • Microsoft Internet Explorer 5.0.1 SP1
  • Microsoft Internet Explorer 5.0.1 SP2
  • Microsoft Internet Explorer 5.5
  • Microsoft Internet Explorer 5.5 SP1
  • Microsoft Internet Explorer 5.5 SP2
  • Microsoft Internet Explorer 6.0


Run all software as a nonprivileged user with minimal access rights.
Browsing the web as a low-privileged user will limit the consequences of malicious code being executed.

Do not follow links provided by unknown or untrusted sources.
Be extremely careful when following links sent by unknown individuals. If possible, always ensure that any email that has been received is solicited before reading the contents.

This vulnerability has been resolved in MSIE 6.0 SP 1. Users are advised to obtain the latest version of MSIE.



Vulnerability discovery credited to Eeye Digital Security.

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