Linux Kernel TCP Selective Acknowledgement Segments Processing Denial of Service Vulnerability [CVE-2019-11478]

CVE Number – CVE-2019-11478

A vulnerability in the Linux Kernel could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition on a targeted system. The vulnerability is due to a resource consumption condition that could occur when the affected software processes TCP Selective Acknowledgment (SACK) segments. An attacker could exploit this vulnerability by repeatedly sending network traffic to the targeted system on a TCP connection with low TCP Maximum Segment Size (MSS). A successful exploit could cause the targeted system to crash, resulting in a DoS condition.Kernel.org has confirmed the vulnerability and released software updates.

Analysis

• To exploit this vulnerability, an attacker must repeatedly send network traffic to the targeted system on a TCP connection with low TCP MSS, making exploitation more difficult in environments that restrict network access from untrusted sources.

Safeguards

• Administrators are advised to apply the appropriate updates.
  
  Administrators are advised to allow only trusted users to have network access.
  
  Administrators are advised to run both firewall and antivirus applications to minimize the potential of inbound and outbound threats.
  
  Administrators may consider using IP-based access control lists (ACLs) to allow only trusted systems to access the affected systems.
  
  Administrators can help protect affected systems from external attacks by using a solid firewall strategy.
  
  Administrators are advised to monitor affected systems.

Vendor Announcements

• Kernel.org has released git commits at the following links: commit 5f3e2bf008c2221478101ee72f5cb4654b9fc363 and commit 967c05aee439e6e5d7d805e195b3a20ef5c433d6

Fixed Software

• Kernel.org has released a software patch at the following link: commit tcp: add tcp_min_snd_mss sysctl