[USN-3434-2] Libidn vulnerability

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Ubuntu Security Notice USN-3434-2
October 23, 2017

libidn vulnerability
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A security issue affects these releases of Ubuntu and its derivatives:

- Ubuntu 12.04 ESM

Summary:

Libidn could be made to crash or run programs if it processed specially
crafted input.

Software Description:
- libidn: implementation of IETF IDN specifications

Details:

USN-3434-1 fixed a vulnerability in  Libidn. This update
provides the corresponding update for Ubuntu 12.04 ESM.

Original advisory details:

 It was discovered that Libidn incorrectly handled decoding certain
 digits. A remote attacker could use this issue to cause Libidn to
 crash, resulting in a denial of service, or possibly execute arbitrary
 code.

Update instructions:

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

Ubuntu 12.04 ESM:
  libidn11                        1.23-2ubuntu0.2

In general, a standard system update will make all the necessary
changes.

References:
  https://www.ubuntu.com/usn/usn-3434-2
  https://www.ubuntu.com/usn/usn-3434-1
  CVE-2017-14062