The gmp plugin in strongSwan before 5.5.3 does not properly validate RSA public keys before calling mpz_powm_sec, which allows remote peers to cause a denial of service (floating point exception and process crash) via a crafted certificate.
https://www.strongswan.org/blog/2017/05/30/strongswan-vulnerability-%28cve-2017-9022%29.html
http://www.ubuntu.com/usn/USN-3301-1