Public Date:
1585011: CVE-2018-3665 Kernel: FPU state information leakage via lazy FPU restore
A Floating Point Unit (FPU) state information leakage flaw was found in the way the Linux kernel saved and restored the FPU state during task switch. Linux kernels that follow the "Lazy FPU Restore" scheme are vulnerable to the FPU state information leakage issue. An unprivileged local attacker could use this flaw to read FPU state bits by conducting targeted cache side-channel attacks, similar to the Meltdown vulnerability disclosed earlier this year.

Find out more about CVE-2018-3665 from the MITRE CVE dictionary dictionary and NIST NVD.


This issue affects the versions of the Linux kernel as shipped with Red Hat Enterprise Linux 5, 6, 7, and Red Hat Enterprise MRG 2. Future kernel updates for Red Hat Enterprise Linux 6, 7, and Red Hat Enterprise MRG 2 may address this issue.

Red Hat Enterprise Linux 5 is now in Production 3 Phase of the support and
maintenance life cycle. This has been rated as having Moderate security
impact and is not currently planned to be addressed in future updates. For
additional information, refer to the Red Hat Enterprise Linux Life

CVSS v3 metrics

CVSS3 Base Score 5.6
CVSS3 Base Metrics CVSS:3.0/AV:L/AC:H/PR:L/UI:N/S:C/C:H/I:N/A:N
Attack Vector Local
Attack Complexity High
Privileges Required Low
User Interaction None
Scope Changed
Confidentiality High
Integrity Impact None
Availability Impact None

Red Hat Security Errata

Platform Errata Release Date
Red Hat Enterprise Linux Extended Update Support 7.4 (kernel) RHSA-2019:1170 2019-05-14
Red Hat Enterprise Linux 6 (kernel) RHSA-2018:2164 2018-07-10
Red Hat Enterprise Linux for Real Time for NFV (v. 7) (kernel-rt) RHSA-2018:1944 2018-06-19
Red Hat MRG Grid for RHEL 6 Server v.2 (kernel-rt) RHSA-2019:1190 2019-05-14
Red Hat Enterprise Linux 7 (kernel) RHSA-2018:1852 2018-06-14
Red Hat MRG Grid for RHEL 6 Server v.2 (kernel-rt) RHSA-2018:2165 2018-07-10

Affected Packages State

Platform Package State
Red Hat Enterprise Linux 8 kernel Not affected
Red Hat Enterprise Linux 7 kernel-alt Not affected
Red Hat Enterprise Linux 5 kernel Will not fix


Red Hat would like to thank Julian Stecklina (, Thomas Prescher (, and Zdenek Sojka ( for reporting this issue.


RHEL-7 will automatically default to (safe) “eager” floating point register restore on Sandy Bridge and newer Intel processors. AMD processors are not affected. You can mitigate this issue on older processors by booting the kernel with the 'eagerfpu=on' parameter to enable eager FPU restore mode. In this mode FPU state is saved and restored for every task/context switch regardless of whether the current process invokes FPU instructions or not. The parameter does not affect performance negatively, and can be applied with no adverse effects to processors that are not affected.

External References

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