Bug 1868453 (CVE-2020-14356) - CVE-2020-14356 kernel: Use After Free vulnerability in cgroup BPF component
Summary: CVE-2020-14356 kernel: Use After Free vulnerability in cgroup BPF component
Alias: CVE-2020-14356
Product: Security Response
Classification: Other
Component: vulnerability
Version: unspecified
Hardware: All
OS: Linux
Target Milestone: ---
Assignee: Red Hat Product Security
QA Contact:
Depends On: 1872015 1872016 1872017 1868479 1868659 1868660
Blocks: 1859200
TreeView+ depends on / blocked
Reported: 2020-08-12 18:10 UTC by Alex
Modified: 2021-06-24 11:50 UTC (History)
47 users (show)

Fixed In Version: kernel 5.7.10
Doc Type: If docs needed, set a value
Doc Text:
A use-after-free flaw was found in the Linux kernel’s cgroupv2 subsystem when rebooting the system. This flaw allows a local user to crash the system or escalate their privileges. The highest threat from this vulnerability is to system availability.
Clone Of:
Last Closed: 2021-05-18 20:34:32 UTC

Attachments (Terms of Use)

System ID Private Priority Status Summary Last Updated
Red Hat Product Errata RHBA-2021:2538 0 None None None 2021-06-23 18:05:55 UTC
Red Hat Product Errata RHBA-2021:2541 0 None None None 2021-06-24 11:50:52 UTC

Description Alex 2020-08-12 18:10:33 UTC
It was found that the Linux kernel's use after free issue could happen during the usage of cgroupv2 (usually when reboot and more likely if virtual machine or docker being used).
After recent commit 090e28b ("netprio_cgroup: Fix unlimited memory leak of v2 cgroups") was merged, the problem could be reproduced much simpler starting with 5.7.x kernels.
The problem introduced with 4.5 kernel, but there is no known way to trigger it, so it was not known until 5.7 kernel.
It could be possible to reproduce the bug by the user without privileges and without reboot if user has an ability to create/close cgroupv2 or this user create a process which is attached to already existing cgroupv2 BPF (but still the user will have to wait till root manually closes cgroupv2 or system is being rebooted).

This commit fixes the problem:

Comment 1 Alex 2020-08-12 18:10:38 UTC

Name: Adam Zabrocki (pi3.com.pl)

Comment 4 Alex 2020-08-12 19:43:34 UTC
Created kernel tracking bugs for this issue:

Affects: fedora-all [bug 1868479]

Comment 5 Justin M. Forbes 2020-08-12 20:44:26 UTC
This was fixed for Fedora in the 5.7.10 stable kernel updates.

Comment 11 Petr Matousek 2020-08-26 12:05:52 UTC

This flaw is rated as a having Moderate impact, because only local user can trigger it and no way to trigger it before reboot happens (until user have complete privileges for accessing cgroupv2).

Comment 18 errata-xmlrpc 2021-05-18 13:20:03 UTC
This issue has been addressed in the following products:

  Red Hat Enterprise Linux 8

Via RHSA-2021:1578 https://access.redhat.com/errata/RHSA-2021:1578

Comment 19 errata-xmlrpc 2021-05-18 14:40:28 UTC
This issue has been addressed in the following products:

  Red Hat Enterprise Linux 8

Via RHSA-2021:1739 https://access.redhat.com/errata/RHSA-2021:1739

Comment 20 Product Security DevOps Team 2021-05-18 20:34:32 UTC
This bug is now closed. Further updates for individual products will be reflected on the CVE page(s):


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