Linux / BSD and UNIX like operating systems includes software from the OpenSSL Project. The OpenSSL is commercial-grade, industry-strength, full-featured Open Source toolkit implementing the Secure Sockets Layer (SSL v2/v3) and Transport Layer Security (TLS v1) protocols as well as general purpose cryptography library.
The Google security team discovered a flaw in the way OpenSSL checked the verification of certificates. An attacker in control of a malicious server, or able to effect a “man in the middle” attack, could present a malformed SSL/TLS signature from a certificate chain to a vulnerable client and bypass validation.
This update has been rated as having important security impact on FreeBSD, all version of Ubuntu / Debian, Red Hat (RHEL), CentOS, Fedora and other open source operating system that depends upon OpenSSL.