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High 1 exploited CVE USN-4915-1 2 CVEs

linux-oem-5.6 vulnerabilities

Published Apr 15, 2021 · Updated Jun 3, 2026

Ecosystem: Ubuntu

Summary

It was discovered that the overlayfs implementation in the Linux kernel did
not properly validate the application of file system capabilities with
respect to user namespaces. A local attacker could use this to gain
elevated privileges. (CVE-2021-3493)

Vincent Dehors discovered that the shiftfs file system in the Ubuntu Linux
kernel did not properly handle faults in copy_from_user() when passing
through ioctls to an underlying file system. A local attacker could use
this to cause a denial of service (memory exhaustion) or execute arbitrary
code. (CVE-2021-3492)

Fixed packages 1

ReleasePackageFixed in
Ubuntu · 20.04 LTS 20.04:LTS linux-oem-5.6 5.6.0-1054.58

Vulnerabilities 2

  • High 8.8
    CVE-2021-3493 Exploited Public exploit EPSS 49%

    The overlayfs implementation in the linux kernel did not properly validate with respect to user namespaces the setting …

    Ubuntu Linux kernel linux-raspi2 linux-hwe Linux Debian Ubuntu
    KEV Oct 20, 2022
  • High 8.8
    CVE-2021-3492 Public exploit

    Ubuntu linux kernel shiftfs file system double free vulnerability

    Shiftfs, an out-of-tree stacking file system included in Ubuntu Linux kernels, did not properly handle faults occurring during copy_from_user() correctly. These could lead to either a double-free situation or memory not being freed at all. An attacker could u…

    Ubuntu Linux kernel linux-raspi2 linux-hwe Linux Ubuntu

References

  • report
    https://ubuntu.com/security/CVE-2021-3492
  • report
    https://ubuntu.com/security/CVE-2021-3493