chmlib, KchmViewer: Stack-based buffer overflow

Background

chmlib is a library for dealing with Microsoft ITSS and CHM format files. KchmViewer is a CHM viewer that includes its own copy of the chmlib library.

Description

Sven Tantau reported about a buffer overflow vulnerability in chmlib. The function “_chm_decompress_block()” does not properly perform boundary checking, resulting in a stack-based buffer overflow.

Impact

By convincing a user to open a specially crafted ITSS or CHM file, using KchmViewer or a program makes use of chmlib, a remote attacker could execute arbitrary code with the privileges of the user running the software.

Workaround

There is no known workaround at this time.

Resolution

All chmlib users should upgrade to the latest version:

 # emerge --sync
 # emerge --ask --oneshot --verbose ">=dev-libs/chmlib-0.37.4"

All KchmViewer users should upgrade to the latest version:

 # emerge --sync
 # emerge --ask --oneshot --verbose ">=app-text/kchmviewer-1.1"