Applications using libxml2 could be made to crash or run programs as your login if they opened a specially crafted file.

=========================================================================Ubuntu Security Notice USN-1334-1
January 19, 2012

libxml2 vulnerabilities
=========================================================================
A security issue affects these releases of Ubuntu and its derivatives:

- Ubuntu 11.10
- Ubuntu 11.04
- Ubuntu 10.10
- Ubuntu 10.04 LTS
- Ubuntu 8.04 LTS

Summary:

Applications using libxml2 could be made to crash or run programs as your
login if they opened a specially crafted file.

Software Description:
- libxml2: GNOME XML library

Details:

It was discovered that libxml2 contained an off by one error. If a user or
application linked against libxml2 were tricked into opening a specially
crafted XML file, an attacker could cause the application to crash or
possibly execute arbitrary code with the privileges of the user invoking
the program. (CVE-2011-0216)

It was discovered that libxml2 is vulnerable to double-free conditions
when parsing certain XML documents. This could allow a remote attacker to
cause a denial of service. (CVE-2011-2821, CVE-2011-2834)

It was discovered that libxml2 did not properly detect end of file when
parsing certain XML documents. An attacker could exploit this to crash
applications linked against libxml2. (CVE-2011-3905)

It was discovered that libxml2 did not properly decode entity references
with long names. If a user or application linked against libxml2 were
tricked into opening a specially crafted XML file, an attacker could cause
the application to crash or possibly execute arbitrary code with the
privileges of the user invoking the program. (CVE-2011-3919)

Update instructions:

The problem can be corrected by updating your system to the following
package versions:

Ubuntu 11.10:
  libxml2                         2.7.8.dfsg-4ubuntu0.1

Ubuntu 11.04:
  libxml2                         2.7.8.dfsg-2ubuntu0.2

Ubuntu 10.10:
  libxml2                         2.7.7.dfsg-4ubuntu0.3

Ubuntu 10.04 LTS:
  libxml2                         2.7.6.dfsg-1ubuntu1.3

Ubuntu 8.04 LTS:
  libxml2                         2.6.31.dfsg-2ubuntu1.7

After a standard system update you need to reboot your computer to make
all the necessary changes.

References:
  https://ubuntu.com/security/notices/USN-1334-1
  CVE-2011-0216, CVE-2011-2821, CVE-2011-2834, CVE-2011-3905,
  CVE-2011-3919

Package Information:
  https://launchpad.net/ubuntu/+source/libxml2/2.7.8.dfsg-4ubuntu0.1
  https://launchpad.net/ubuntu/+source/libxml2/2.7.8.dfsg-2ubuntu0.2
  https://launchpad.net/ubuntu/+source/libxml2/2.7.7.dfsg-4ubuntu0.3
  https://launchpad.net/ubuntu/+source/libxml2/2.7.6.dfsg-1ubuntu1.3
  https://launchpad.net/ubuntu/+source/libxml2/2.6.31.dfsg-2ubuntu1.7