Vulnerability Note VU#643615

libpng fails to limit number of rows in header

Several versions of libpng through 1.4.2 (and through 1.2.43 in the older series) contain a bug whereby progressive applications such as web browsers (or the rpng2 demo app included in libpng) could receive an extra row of image data beyond the height reported in the header, potentially leading to an out-of-bounds write to memory (depending on how the application is written) and the possibility of execution of an attacker's code with the privileges of the libpng user (including remote compromise in the case of a libpng-based browser visiting a hostile web site).

Note that this issue affects all versions of libpng prior to 1.2.44 and libpng-1.4.3 and all libpng-1.0.X.

II. Impact

The PNG Development Group has issued an upgrade to address this issue. See libpng version 1.2.44 and 1.4.3 for more information.
A workaround for vendors of products or applications using derivative versions of libpng is to check for row_num greater than or equal to the image height, at the beginning of the user-supplied row callback function.

Vendor Information

http://libpng.org/pub/png/libpng.html
http://libpng.git.sourceforge.net/git/gitweb.cgi?p=libpng/libpng;a=commitdiff;h=188eb6b42602bf7d7ae708a21897923b6a83fe7c#patch18
https://bugzilla.redhat.com/show_bug.cgi?id=608238
http://admin.fedoraproject.org/updates/libpng-1.2.44-1.fc13
http://admin.fedoraproject.org/updates/libpng-1.2.44-1.fc12

Credit

This issue was reported by the PNG Development Group in libpng version 1.2.44 and 1.4.3.

This document was written by Michael Orlando.

Other Information

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