A strongSwan security update has been released for Ubuntu Linux 18.04 LTS, 20.04 LTS, 21.04, and 21.10.

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Ubuntu Security Notice USN-5111-1
October 19, 2021

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

- Ubuntu 21.10
- Ubuntu 21.04
- Ubuntu 20.04 LTS
- Ubuntu 18.04 LTS

Summary:

Several security issues were fixed in strongSwan.

Software Description:
- strongswan: IPsec VPN solution

Details:

It was discovered that strongSwan incorrectly handled certain RSASSA-PSS
signatures. A remote attacker could use this issue to cause strongSwan to
crash, resulting in a denial of service. (CVE-2021-41990)

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 21.10:
libstrongswan 5.9.1-1ubuntu3.1
strongswan 5.9.1-1ubuntu3.1

Ubuntu 21.04:
libstrongswan 5.9.1-1ubuntu1.2
strongswan 5.9.1-1ubuntu1.2

Ubuntu 20.04 LTS:
libstrongswan 5.8.2-1ubuntu3.3
strongswan 5.8.2-1ubuntu3.3

Ubuntu 18.04 LTS:
libstrongswan 5.6.2-1ubuntu2.7
strongswan 5.6.2-1ubuntu2.7

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

References:
  https://ubuntu.com/security/notices/USN-5111-1
CVE-2021-41990, CVE-2021-41991

Package Information:
  https://launchpad.net/ubuntu/+source/strongswan/5.9.1-1ubuntu3.1
  https://launchpad.net/ubuntu/+source/strongswan/5.9.1-1ubuntu1.2
  https://launchpad.net/ubuntu/+source/strongswan/5.8.2-1ubuntu3.3
  https://launchpad.net/ubuntu/+source/strongswan/5.6.2-1ubuntu2.7