CVE-2018-5390: Vulnerability in Linux Kernel allows for DOS Attacks
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CVE-2018-5390: Vulnerabilidade no Kernel Linux permite ataques de DoS




A vulnerabilidade foi identificada no Kernel Linux (versão 4.9+) que é monitorado no consultivo CVE-2018-5390. Ele enumera várias condições que permitem que criminosos para modificar pacotes que levam à coordenação dos DoS (Negação de serviço) ataques.

CVE-2018-5390 Advisory Tracks DoS Attack Linux Kernel Vulnerability

An email message, posted by Juha-Matti Tilli reported yet another security related issue in the Linux Kernel. The CVE-2018-5390 advisory is a newly published security bulletin which gives details upon a Linux Kernel vulnerability. The document shows that versions 4.9+ can be affected by specific service conditions that can lead to a DoS (Negação de serviço) ataques. The exact nature of the issue is related to a modification of behaviour by the users. The kernel can be forced into making calls to two functions for every incoming packet:

  • tcp_collapse_ofo_queue() — This routine collapses an out-of-order queue whenever the memory quota for the receive queue is full to make space for the arrived data segment. This is used for buffer control.
  • tcp_prune_ofo_queue() — This is a prune function for the network packets. It is used during the queue operations.
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Every incoming packet can be modified into going through these two functions. This can lead to a behaviour pattern leading to a Denial of service possibility. The attackers can induce such conditions by sending out modified packets within the ongoing TCP network sessions. The analysis shows that maintaining this state requires a continuous two-way TCP sessions via a reachable open port on the target machine. This means that the attacks can only be performed via real IP addresses, spoofed addresses cannot be used.




At the time of writing this article the device vendors have not published any patches. Once they are ready the appropriate bulletins and updates will be issued both to end users and device owners. A patch series is available which implements a fix to the problem by limiting the cpu cycles to a certain limit which in the end renders the bug non-critical. In the future the developers might proceed with further fixes such as disconnecting or black-holing proven malicious flows.

Atualizar! It appears that the the necessary updates were included in the Linux Kernel before the security announcement were made. They are found in the 4.9.116 e 4.17.11 kernel releases.

By applying the latest Linux Kernel update users will be able to protect themselves from incoming attacks.

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Martin Beltov

Martin formou-se na publicação da Universidade de Sofia. Como a segurança cibernética entusiasta ele gosta de escrever sobre as ameaças mais recentes e mecanismos de invasão.

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2 Comentários

  1. AvatarNixon

    Our server running the kernel version “4.4.0-133-generic” / Ubuntu 14.04.5 LTS Operating system.
    4.4.0-133-genericis the latest kernel update available in the official repositories.

    1) I just wanted to know if this vulnerability is only affected to 4.9.x kernel?
    2) Any action required on the 4.4.x kernel?
    3) Is this kernel is not impacted with this vulnerability.

    Reply
    1. AvatarMartin Beltov (pós autor)

      Hello Nixon,

      So far the information that we have found about the matter is that the bug impacts only later releases of the Linux Kernel release. As far as we know the 4.4.x family is not affected. However it would be best to ask the Ubuntu security team for confirmation.

      Reply

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