Openswan is an implementation of IPsec for Linux.
Multiple vulnerabilities have been discovered in Openswan:
A remote attacker could exploit these vulnerabilities by sending specially crafted R_U_THERE or R_U_THERE_ACK packets, or a specially crafted X.509 certificate containing a malicious Relative Distinguished Name (RDN), UTCTIME string or GENERALIZEDTIME string to cause a Denial of Service of the pluto IKE daemon.
There is no known workaround at this time.
All Openswan users should upgrade to the latest version:
# emerge --sync
# emerge --ask --oneshot --verbose ">=net-misc/openswan-2.4.15"