Updated openswan packages that fix one security issue are now available for Red Hat Enterprise Linux 5 and 6. The Red Hat Security Response Team has rated this update as having important security impact. A Common Vulnerability Scoring System base score, which gives a detailed severity rating, is available from the CVE link in the References section. Openswan is a free implementation of Internet Protocol Security and Internet Key Exchange . IPsec uses strong cryptography to provide both authentication and encryption services. These services allow you to build secure tunnels through untrusted networks. When using Opportunistic Encryption, Openswan's pluto IKE daemon requests DNS TXT records to obtain public RSA keys of itself and its peers. A buffer overflow flaw was found in Openswan. If Opportunistic Encryption were enabled and an RSA key configured, an attacker able to cause a system to perform a DNS lookup for an attacker-controlled domain containing malicious records could cause Openswan's pluto IKE daemon to crash or, potentially, execute arbitrary code with root privileges. With "oe=yes" but no RSA key configured, the issue can only be triggered by attackers on the local network who can control the reverse DNS entry of the target system. Opportunistic Encryption is disabled by default. This issue was discovered by Florian Weimer of the Red Hat Product Security Team. All users of openswan are advised to upgrade to these updated packages, which contain backported patches to correct this issue. After installing this update, the ipsec service will be restarted automatically.