Stephane Chazelas discovered a vulnerability in bash, the GNU Bourne-Again Shell, related to how environment variables are processed. In many common configurations, this vulnerability is exploitable over the network, especially if bash has been configured as the system shell.
For the stable distribution (wheezy), this problem has been fixed in version 4.2+dfsg-0.1+deb7u1.
We recommend that you upgrade your bash packages.
Further information about Debian Security Advisories, how to apply these updates to your system and frequently asked questions can be found at: https://www.debian.org/security/