It was discovered that libxml2, the GNOME XML library, didn't correctly handle long entity names. This could allow the execution of arbitrary code via a malicious XML file.
For the stable distribution (etch), this problem has been fixed in version 2.6.27.dfsg-5.
For the unstable distribution (sid), this problem has been fixed in version 2.6.32.dfsg-4.
We recommend that you upgrade your libxml2 package.