Security Experts:

'SegmentSmack' Flaw in Linux Kernel Allows Remote DoS Attacks

A vulnerability in the Linux kernel can allow a remote attacker to trigger a denial-of-service (DoS) condition by sending specially crafted packets to the targeted system. The flaw could impact many companies.

The security hole, classified as high severity, has been named SegmentSmack and is tracked as CVE-2018-5390. The issue was discovered by Juha-Matti Tilli of Aalto University and Nokia’s Bell Labs.

The vulnerability exists due to the way versions 4.9 and later of the Linux kernel handle specially crafted TCP packets. Linux kernel developers have released a patch that should address the problem.

“A remote attacker could use this flaw to trigger time and calculation expensive calls to tcp_collapse_ofo_queue() and tcp_prune_ofo_queue() functions by sending specially modified packets within ongoing TCP sessions which could lead to a CPU saturation and hence a denial of service on the system,” Red Hat explained in an advisory for SegmentSmack. “Maintaining the denial of service condition requires continuous two-way TCP sessions to a reachable open port, thus the attacks cannot be performed using spoofed IP addresses.”

Red Hat says all its products with moderately new Linux kernel versions are affected. The company has not identified any workarounds or mitigations besides the kernel patches.

CERT/CC has also published an advisory for SegmentSmack. The organization believes the vulnerability could impact tens of major vendors, including Amazon, Apple, BlackBerry, Cisco, Dell, Google, HP, IBM, Lenovo, Microsoft and several cybersecurity and networking solutions providers.

Amazon Web Services (AWS) says it has launched an investigation into the impact of the flaw on its products.

“AWS is aware of a recently-disclosed security issue, commonly referred to as SegmentSmack, which affects the TCP processing subsystem of several popular operating systems including Linux,” AWS said. “AWS services are operating normally. We will post a further update as soon as one is available.”

SUSE Linux has also released patches, but the organization says the vulnerability only affects SUSE Linux Enterprise 15.

Related: Privilege Escalation Bug Lurked in Linux Kernel for 8 Years

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Related: Vulnerabilities Found in Linux 'Beep' Tool

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Eduard Kovacs (@EduardKovacs) is a contributing editor at SecurityWeek. He worked as a high school IT teacher for two years before starting a career in journalism as Softpedia’s security news reporter. Eduard holds a bachelor’s degree in industrial informatics and a master’s degree in computer techniques applied in electrical engineering.