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Ubuntu Security Notice USN-2815-1
November 19, 2015

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

- Ubuntu 15.10
- Ubuntu 15.04
- Ubuntu 14.04 LTS
- Ubuntu 12.04 LTS

Summary:

libpng could be made to crash or run programs as your login if it
opened a specially crafted file.

Software Description:
- libpng: PNG (Portable Network Graphics) file library

Details:

Mikulas Patocka discovered that libpng incorrectly handled certain large
fields. If a user or automated system using libpng were tricked into
opening a specially crafted image, an attacker could exploit this to cause
libpng to crash, leading to a denial of service. This issue only affected
Ubuntu 12.04 LTS. (CVE-2012-3425)

Qixue Xiao discovered that libpng incorrectly handled certain time values.
If a user or automated system using libpng were tricked into opening a
specially crafted image, an attacker could exploit this to cause libpng to
crash, leading to a denial of service. (CVE-2015-7981)

It was discovered that libpng incorrectly handled certain small bit-depth
values. If a user or automated system using libpng were tricked into
opening a specially crafted image, an attacker could exploit this to cause
a denial of service or execute code with the privileges of the user
invoking the program. (CVE-2015-8126)

Update instructions:

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

Ubuntu 15.10:
  libpng12-0                      1.2.51-0ubuntu3.15.10.1

Ubuntu 15.04:
  libpng12-0                      1.2.51-0ubuntu3.15.04.1

Ubuntu 14.04 LTS:
  libpng12-0                      1.2.50-1ubuntu2.14.04.1

Ubuntu 12.04 LTS:
  libpng12-0                      1.2.46-3ubuntu4.1

After a standard system update you need to restart your session to make
all the necessary changes.

References:
  http://www.ubuntu.com/usn/usn-2815-1
  CVE-2012-3425, CVE-2015-7981, CVE-2015-8126

Package Information:
  https://launchpad.net/ubuntu/+source/libpng/1.2.51-0ubuntu3.15.10.1
  https://launchpad.net/ubuntu/+source/libpng/1.2.51-0ubuntu3.15.04.1
  https://launchpad.net/ubuntu/+source/libpng/1.2.50-1ubuntu2.14.04.1
  https://launchpad.net/ubuntu/+source/libpng/1.2.46-3ubuntu4.1