CVE-2021-3492: Ubuntu linux kernel shiftfs file system double free vulnerability

Published Apr 17, 2021
·
Updated

Last updated 12 October 2026

Other sources

Shiftfs, an out-of-tree stacking file system included in Ubuntu Linux kernels, did not properly handle faults occurring during copyfromuser() correctly. These could lead to either a double-free situation or memory not being freed at all. An attacker could use this to cause a denial of service (kernel memory exhaustion) or gain privileges via executing arbitrary code. AKA ZDI-CAN-13562.

— Launchpad

This vulnerability allows local attackers to escalate privileges on affected installations of Canonical Ubuntu. An attacker must first obtain the ability to execute high-privileged code on the target system in order to exploit this vulnerability. The specific flaw exists within the ShiftFS module. The issue results from the lack of validating the existence of an object prior to performing further free operations on the object. An attacker can leverage this vulnerability to escalate privileges and execute code in the context of the kernel.

— ZDI

Affected Software

52 affected componentsFixes available
Canonical Ubuntu Linux<18.04
Canonical Ubuntu Linux>=18.04.1<20.04
Canonical Ubuntu Linux<20.10
Canonical Ubuntu
debian/linux
6.1.176-16.1.190-16.12.107-16.12.113-17.2.12-17.2.13-1
ubuntu/linux-hwe-edge*
ubuntu/linux-aws-5.4<5.4.0-1045.47~18.04.1
5.4.0-1045.47~18.04.1
ubuntu/linux-azure-5.4<5.4.0-1046.48~18.04.1
5.4.0-1046.48~18.04.1
ubuntu/linux-gcp-5.4<5.4.0-1042.45~18.04.1
5.4.0-1042.45~18.04.1
ubuntu/linux-gke-5.3<5.3.0-1042.45
5.3.0-1042.45
ubuntu/linux-gke-5.4<5.4.0-1042.44~18.04.1
5.4.0-1042.44~18.04.1
ubuntu/linux-gkeop-5.4<5.4.0-1014.15~18.04.1
5.4.0-1014.15~18.04.1
ubuntu/linux-hwe<5.3.0-73.69
5.3.0-73.69
ubuntu/linux-hwe-5.4<5.4.0-72.80~18.04.1
5.4.0-72.80~18.04.1
ubuntu/linux-oracle-5.4<5.4.0-1043.46~18.04.1
5.4.0-1043.46~18.04.1
ubuntu/linux-raspi-5.4<5.4.0-1034.37~18.04.1
5.4.0-1034.37~18.04.1
ubuntu/linux-raspi2-5.3<5.3.0-1039.41
5.3.0-1039.41
ubuntu/linux-aws-5.0*
ubuntu/linux-aws-5.3*
ubuntu/linux-azure*
ubuntu/linux-azure-5.3*
ubuntu/linux-azure-edge*
ubuntu/linux-gcp*
ubuntu/linux-gcp-5.3*
ubuntu/linux-gcp-edge*
ubuntu/linux-hwe-edge*
ubuntu/linux-oracle-5.0*
ubuntu/linux-oracle-5.3*
ubuntu/linux<5.4.0-72.80
5.4.0-72.80
ubuntu/linux-aws<5.4.0-1045.47
5.4.0-1045.47
ubuntu/linux-azure<5.4.0-1046.48
5.4.0-1046.48
ubuntu/linux-gcp<5.4.0-1042.45
5.4.0-1042.45
ubuntu/linux-gke<5.4.0-1042.44
5.4.0-1042.44
ubuntu/linux-gkeop<5.4.0-1014.15
5.4.0-1014.15
ubuntu/linux-hwe-5.8<5.8.0-50.56~20.04.1
5.8.0-50.56~20.04.1
ubuntu/linux-kvm<5.4.0-1038.39
5.4.0-1038.39
ubuntu/linux-oem-5.10<5.10.0-1022.23
5.10.0-1022.23
ubuntu/linux-oem-5.6<5.6.0-1054.58
5.6.0-1054.58
ubuntu/linux-oracle<5.4.0-1043.46
5.4.0-1043.46
ubuntu/linux-raspi<5.4.0-1034.37
5.4.0-1034.37
ubuntu/linux-riscv-5.8<5.8.0-22.24~20.04.1
5.8.0-22.24~20.04.1
ubuntu/linux-raspi2*
ubuntu/linux-aws-fips<5.4.0-1069.73+fips2
5.4.0-1069.73+fips2
ubuntu/linux-azure-fips<5.4.0-1073.76+fips1
5.4.0-1073.76+fips1
ubuntu/linux-gcp-fips<5.4.0-1067.71~20.04.1
5.4.0-1067.71~20.04.1
ubuntu/linux-aws-fips*
ubuntu/linux-azure-fips*
ubuntu/linux-gcp-fips*
ubuntu/linux-intel-iot-realtime*
ubuntu/linux-realtime*
ubuntu/linux-raspi-realtime*
ubuntu/linux-vmware*

Remediation

Recommended actions to resolve this vulnerability, in priority order.

  1. Upgrade

    Upgrade debian/linux to a version that resolves this vulnerability.

    Fixed in 6.1.176-1Fixed in 6.1.190-1Fixed in 6.12.107-1Fixed in 6.12.113-1Fixed in 7.2.12-1Fixed in 7.2.13-1
  2. Upgrade

    Upgrade ubuntu/linux-aws-5.4 to a version that resolves this vulnerability.

    Fixed in 5.4.0-1045.47~18.04.1
  3. Upgrade

    Upgrade ubuntu/linux-azure-5.4 to a version that resolves this vulnerability.

    Fixed in 5.4.0-1046.48~18.04.1
  4. Upgrade

    Upgrade ubuntu/linux-gcp-5.4 to a version that resolves this vulnerability.

    Fixed in 5.4.0-1042.45~18.04.1
  5. Upgrade

    Upgrade ubuntu/linux-gke-5.3 to a version that resolves this vulnerability.

    Fixed in 5.3.0-1042.45
  6. Upgrade

    Upgrade ubuntu/linux-gke-5.4 to a version that resolves this vulnerability.

    Fixed in 5.4.0-1042.44~18.04.1
  7. Upgrade

    Upgrade ubuntu/linux-gkeop-5.4 to a version that resolves this vulnerability.

    Fixed in 5.4.0-1014.15~18.04.1
  8. Upgrade

    Upgrade ubuntu/linux-hwe to a version that resolves this vulnerability.

    Fixed in 5.3.0-73.69
  9. Upgrade

    Upgrade ubuntu/linux-hwe-5.4 to a version that resolves this vulnerability.

    Fixed in 5.4.0-72.80~18.04.1
  10. Upgrade

    Upgrade ubuntu/linux-oracle-5.4 to a version that resolves this vulnerability.

    Fixed in 5.4.0-1043.46~18.04.1
  11. Upgrade

    Upgrade ubuntu/linux-raspi-5.4 to a version that resolves this vulnerability.

    Fixed in 5.4.0-1034.37~18.04.1
  12. Upgrade

    Upgrade ubuntu/linux-raspi2-5.3 to a version that resolves this vulnerability.

    Fixed in 5.3.0-1039.41
  13. Upgrade

    Upgrade ubuntu/linux to a version that resolves this vulnerability.

    Fixed in 5.4.0-72.80
  14. Upgrade

    Upgrade ubuntu/linux-aws to a version that resolves this vulnerability.

    Fixed in 5.4.0-1045.47
  15. Upgrade

    Upgrade ubuntu/linux-azure to a version that resolves this vulnerability.

    Fixed in 5.4.0-1046.48
  16. Upgrade

    Upgrade ubuntu/linux-gcp to a version that resolves this vulnerability.

    Fixed in 5.4.0-1042.45
  17. Upgrade

    Upgrade ubuntu/linux-gke to a version that resolves this vulnerability.

    Fixed in 5.4.0-1042.44
  18. Upgrade

    Upgrade ubuntu/linux-gkeop to a version that resolves this vulnerability.

    Fixed in 5.4.0-1014.15
  19. Upgrade

    Upgrade ubuntu/linux-hwe-5.8 to a version that resolves this vulnerability.

    Fixed in 5.8.0-50.56~20.04.1
  20. Upgrade

    Upgrade ubuntu/linux-kvm to a version that resolves this vulnerability.

    Fixed in 5.4.0-1038.39
  21. Upgrade

    Upgrade ubuntu/linux-oem-5.10 to a version that resolves this vulnerability.

    Fixed in 5.10.0-1022.23
  22. Upgrade

    Upgrade ubuntu/linux-oem-5.6 to a version that resolves this vulnerability.

    Fixed in 5.6.0-1054.58
  23. Upgrade

    Upgrade ubuntu/linux-oracle to a version that resolves this vulnerability.

    Fixed in 5.4.0-1043.46
  24. Upgrade

    Upgrade ubuntu/linux-raspi to a version that resolves this vulnerability.

    Fixed in 5.4.0-1034.37
  25. Upgrade

    Upgrade ubuntu/linux-riscv-5.8 to a version that resolves this vulnerability.

    Fixed in 5.8.0-22.24~20.04.1
  26. Upgrade

    Upgrade ubuntu/linux-aws-fips to a version that resolves this vulnerability.

    Fixed in 5.4.0-1069.73+fips2
  27. Upgrade

    Upgrade ubuntu/linux-azure-fips to a version that resolves this vulnerability.

    Fixed in 5.4.0-1073.76+fips1
  28. Upgrade

    Upgrade ubuntu/linux-gcp-fips to a version that resolves this vulnerability.

    Fixed in 5.4.0-1067.71~20.04.1

Event History

Apr 15, 2021
CVE Published
via Ubuntu·12:00 AM
Data Sourced
via Ubuntu·12:00 AM
RemedyDescriptionSeverityAffected Software
Data Sourced
via OSV·05:00 PM
DescriptionSeverityAffected Software
Apr 17, 2021
CVE Published
via MITRE·04:20 AM
Data Sourced
via MITRE·04:20 AM
DescriptionSeverityWeakness
Data Sourced
via NVD·05:15 AM
RemedyDescriptionSeverityWeaknessAffected Software
Apr 21, 2021
Advisory Published
via ZDI·12:00 AM
Data Sourced
via ZDI·12:00 AM
DescriptionSeverityAffected Software
Jun 28, 2021
Exploit Published
via GitHub·09:43 AM

Frequently Asked Questions

1

What is the severity of CVE-2021-3492?

CVE-2021-3492 has a medium severity level due to potential memory issues leading to vulnerabilities.

2

How do I fix CVE-2021-3492?

You can fix CVE-2021-3492 by upgrading to the recommended kernel versions such as 5.10.223-1, 5.10.226-1, 6.1.119-1, 6.1.123-1, 6.12.11-1, or 6.12.12-1.

3

Which versions of Ubuntu are affected by CVE-2021-3492?

CVE-2021-3492 affects Ubuntu versions from 18.04 up to 20.10.

4

What type of vulnerabilities does CVE-2021-3492 introduce?

CVE-2021-3492 may introduce double-free situations or situations where memory is not freed, increasing the risk of an attack.

5

Is CVE-2021-3492 an issue with just Ubuntu?

CVE-2021-3492 specifically affects the Shiftfs stacking file system in Ubuntu Linux kernels.

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