strongSwan could be made to crash or hang if it received specially crafted network traffic.

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Ubuntu Security Notice USN-3397-1
August 21, 2017

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

- Ubuntu 17.04
- Ubuntu 16.04 LTS
- Ubuntu 14.04 LTS

Summary:

strongSwan could be made to crash or hang if it received specially
crafted network traffic.

Software Description:
- strongswan: IPsec VPN solution

Details:

It was discovered that strongSwan incorrectly handled verifying
specific RSA signatures. A remote attacker could use this issue
to cause strongSwan to crash, resulting in a denial of service.

Update instructions:

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

Ubuntu 17.04:
  libstrongswan                   5.5.1-1ubuntu3.2
  strongswan                      5.5.1-1ubuntu3.2

Ubuntu 16.04 LTS:
  libstrongswan                   5.3.5-1ubuntu3.4
  strongswan                      5.3.5-1ubuntu3.4

Ubuntu 14.04 LTS:
  libstrongswan                   5.1.2-0ubuntu2.7
  strongswan                      5.1.2-0ubuntu2.7

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

References:
  https://www.ubuntu.com/usn/usn-3397-1
  CVE-2017-11185

Package Information:
  https://launchpad.net/ubuntu/+source/strongswan/5.5.1-1ubuntu3.2
  https://launchpad.net/ubuntu/+source/strongswan/5.3.5-1ubuntu3.4
  https://launchpad.net/ubuntu/+source/strongswan/5.1.2-0ubuntu2.7