It was found that OpenSSL was vulnerable to a SSL/TLS MITM vulnerability. An attacker using a carefully crafted handshake can force the use of weak keying material in OpenSSL SSL/TLS clients and servers. This can be exploited by a Man-in-the-middle (MITM) attack where the attacker can decrypt and modify traffic from the attacked client and server.
As per the upstream advisory:
The attack can only be performed between a vulnerable client and server. OpenSSL clients are vulnerable in all versions of OpenSSL. Servers are only known to be vulnerable in OpenSSL 1.0.1 and 1.0.2-beta1. Users of OpenSSL servers earlier than 1.0.1 are advised to upgrade as a precaution.
OpenSSL 0.9.8 SSL/TLS users (client and/or server) should upgrade to 0.9.8za. OpenSSL 1.0.0 SSL/TLS users (client and/or server) should upgrade to 1.0.0m. OpenSSL 1.0.1 SSL/TLS users (client and/or server) should upgrade to 1.0.1h.
Acknowledgements:
Red Hat would like to thank the OpenSSL project for reporting this issue. Upstream acknowledges KIKUCHI Masashi of Lepidum as the original reporter of this issue.
Siemens RuggedCom Rugged Operating System (ROS) before 3.12, ROX I OS through 1.14.5, ROX II OS through 2.3.0, and RuggedMax OS through 4.2.1.4621.22 use hardcoded private keys for SSL and SSH communication, which makes it easier for man-in-the-middle attackers to spoof servers and decrypt network traffic by leveraging the availability of these keys within ROS files at all customer installations.
OpenBSD kernel version <= 6.5 can be forced to create long chains of TCP SACK holes that causes very expensive calls to tcpsackoption() for every incoming SACK packet which can lead to a denial of service.
An excessive resource consumption flaw was found in the way the Linux kernel's networking subsystem processed TCP Selective Acknowledgment (SACK) segments. While processing SACK segments, the Linux kernel's socket buffer (SKB) data structure becomes fragmented, which leads to increased resource utilization to traverse and process these fragments as further SACK segments are received on the same TCP connection. A remote attacker could use this flaw to cause a denial of service (DoS) by sending a crafted sequence of SACK segments on a TCP connection.