Linux Kernel TCP Reassembly Algorithm Remote Denial of Service Vulnerability [CVE-2018-5390]

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 exists because the affected software uses an inefficient TCP reassembly algorithm. An attacker could exploit this vulnerability by sending TCP packets within ongoing sessions that submit malicious input to a targeted system. A successful exploit could trigger resource-intensive time and calculation calls to the tcp_collapse_ofo_queue() and tcp_prune_ofo_queue() functions of the software, which could consume excessive CPU resources, resulting in a DoS condition.

Kernel.org has confirmed the vulnerability and released software updates.

CVE Number – CVE-2018-5390

Analysis
  • To exploit this vulnerability, an attacker must send TCP packets that submit malicious input to the targeted system, making exploitation more difficult in environments that restrict network access from untrusted sources.

    In order to maintain the DoS condition after a successful exploit, the attacker must maintain continuous two-way TCP sessions to an open port on the targeted system. An attacker cannot exploit this vulnerability by using spoofed IP addresses.

    This vulnerability is known as a SegmentSmack attack.

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
Fixed Software




Duncan is a technology professional with over 20 years experience of working in various IT roles. He also has a wide range of other skills in radio, electronics and telecommunications.

Duncan Newell

Duncan is a technology professional with over 20 years experience of working in various IT roles. He also has a wide range of other skills in radio, electronics and telecommunications.

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