K78234183 : Linux SACK Panic vulnerability CVE-2019-11477

Security Advisory Description

Jonathan Looney discovered that the TCP_SKB_CB(skb)->tcp_gso_segs value was subject to an integer overflow in the Linux kernel when handling TCP Selective Acknowledgments (SACKs). A remote attacker could use this to cause a denial of service. This has been fixed in stable kernel releases 4.4.182, 4.9.182, 4.14.127, 4.19.52, 5.1.11, and is fixed in commit 3b4929f65b0d8249f19a50245cd88ed1a2f78cff. (CVE-2019-11477)

Impact

BIG-IP

The BIG-IP system has no exposure to this vulnerability within the Traffic Management Microkernel (TMM), including virtual servers and virtual IP addresses (also known as the data plane). However, the BIG-IP system is vulnerable via the self IP addresses and the management interface (also known as the control plane). A remote attacker can exploit this vulnerability to cause a denial of service (DoS) by sending a sequence of specially crafted TCP packets.

Backend systems accessed via a FastL4 virtual server

By its nature as a full-proxy, the BIG-IP system protects backend systems accessed through a standard virtual server, as any attacker’s TCP connection would be terminated at the BIG-IP system. However, backend systems accessed via a FastL4 virtual server (a virtual server configured with a FastL4 profile) are exposed by default as the attack traffic is forwarded as-is to the backend system.

Traffix SDC

A remote attacker can exploit this vulnerability to cause a denial of service by sending a sequence of specially crafted TCP SACK packets.