A strongSwan security update has been released for Ubuntu Linux 14.04 ESM and 16.04 ESM.

USN-5111-2: strongSwan vulnerability

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Ubuntu Security Notice USN-5111-2
October 19, 2021

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

- Ubuntu 16.04 ESM
- Ubuntu 14.04 ESM

Summary:

Several security issues were fixed in strongSwan.

Software Description:
- strongswan: IPsec VPN solution

Details:

USN-5111-1 fixed a vulnerability in strongSwan. This update provides
the corresponding update for Ubuntu 14.04 ESM and Ubuntu 16.04 ESM.

Original advisory details:

It was discovered that strongSwan incorrectly handled replacing
certificates in the cache. A remote attacker could use this issue to cause
strongSwan to crash, resulting in a denial of service, or possibly execute
arbitrary code. (CVE-2021-41991)

Update instructions:

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

Ubuntu 16.04 ESM:
libstrongswan 5.3.5-1ubuntu3.8+esm1
strongswan 5.3.5-1ubuntu3.8+esm1

Ubuntu 14.04 ESM:
libstrongswan 5.1.2-0ubuntu2.11+esm1
strongswan 5.1.2-0ubuntu2.11+esm1

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

References:
  https://ubuntu.com/security/notices/USN-5111-2
  https://ubuntu.com/security/notices/USN-5111-1
CVE-2021-41991