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Rewterz Threat Advisory – Ubuntu Shiftfs and Overlays Vulnerabilities

Severity

High

Analysis Summary

CVE-2021-3492

A double-free flaw in the copy_from_user() function allows an attacker to execute arbitrary code on the system in shiftfs (out-of-tree stacking file system). The attacker can exploit this vulnerability by sending specially crafted ioctls requests to cause kernel memory consumption (denial of service) in the system or execute arbitrary codes.

CVE-2021-3493

In the overlayfs stacking file system in the kernel, an authenticated attacker can gain elevated privileges on the system caused by the improper validation of filing capabilities against user namespaces. The attacker can exploit this vulnerability by sending specially crafted requests along with a patch carried in the Ubuntu kernel to gain elevated privileges.

Impact

  • Denial of Service
  • Gain Escalated privileges
  • Gain access

Affected Vendors

Ubuntu

Affected Products

  • Ubuntu Ubuntu 20.04 LTS
  • Ubuntu Ubuntu 20.10
  • Linux Kernel 5.10
  • Linux Kernel 5.11

Remediation

Download the latest patches for Ubuntu and refer to the Ubuntu website for information on upgrades or suggested workarounds at

https://git.launchpad.net/~ubuntu-kernel/ubuntu/+source/linux/+git/groovy/commit/?id=5c4ddd2d104e5561724c636c9a83ab722255dc2e

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