Computing Processor PortSmash Side-Channel Information Disclosure Vulnerability [CVE-2018-5407]

CVE number – CVE-2018-5407

A vulnerability in the design of most modern CPUs using Simultaneous Multithreading (SMT)/Hyper-Threading could allow a local attacker to access sensitive information on a targeted system.

The vulnerability exists in the execution engine sharing functionality on SMT/Hyper-Threading architectures and is due to port contention. An attacker with sufficient system access to execute code on a parallel thread of a targeted CPU core could exploit the vulnerability by targeting ports to stacks of execution units in order to create a high-resolution timing side-channel. A successful exploit could allow the attacker to use side-channel timing attacks to access sensitive information on the system.Proof-of-concept (PoC) code that demonstrates an exploit of this vulnerability is publicly available.Intel has not confirmed the vulnerability or released software updates. OpenSSL has confirmed the vulnerability and released software updates.


  • To exploit this vulnerability, the attacker must have user-level access to the targeted system. This access requirement could reduce the likelihood of a successful exploit.

    Systems utilizing SMT/Hyper-Threading are affected, including systems that use modern processors manufactured by Intel.

    Cisco is aware of recently published security research related to side-channel timing attacks in modern CPU architectures. Our team is following our well-established process to investigate all aspects of the issue and evaluate any potential impact on Cisco products. If something new is found that our customers need to be aware of and respond to, we will share it through our established PSIRT disclosure processes.


  • Administrators are advised to contact the vendor regarding future updates and releases.

    Administrators are advised to allow only trusted users to access local systems.

    Administrators are advised to allow only privileged users to access administration or management systems.

    Administrators are advised to monitor critical systems.

Vendor Announcements

  • At the time this alert was first published, Intel had not confirmed the vulnerability. OpenSSL has released a security advisory at the following link: CVE-2018-5407

Fixed Software

  • At the time this alert was first published, Intel had not released software updates.OpenSSL has released software updates at the following link: OpenSSL Downloads

Duncan Newell

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

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