CVE-2021-4155: Medium severity Linux Linux kernel vulnerability

Published Dec 22, 2021
·
Updated

A data leak flaw was found in the way XFSIOCALLOCSP IOCTL in the XFS filesystem allowed for size increase of files with unaligned size. A local attacker could use this flaw to leak data on the XFS filesystem otherwise not accessible to them.

Affected Software

18 affected componentsFixes available
redhat/kernel<0:2.6.32-754.47.1.el6
0:2.6.32-754.47.1.el6
redhat/kernel-rt<0:3.10.0-1160.59.1.rt56.1200.el7
0:3.10.0-1160.59.1.rt56.1200.el7
redhat/kernel<0:3.10.0-1160.59.1.el7
0:3.10.0-1160.59.1.el7
redhat/kernel<0:3.10.0-514.97.1.el7
0:3.10.0-514.97.1.el7
redhat/kernel<0:3.10.0-693.96.1.el7
0:3.10.0-693.96.1.el7
redhat/kernel<0:3.10.0-957.88.1.el7
0:3.10.0-957.88.1.el7
redhat/kernel<0:3.10.0-1062.63.1.el7
0:3.10.0-1062.63.1.el7
redhat/kernel-rt<0:4.18.0-348.12.2.rt7.143.el8_5
0:4.18.0-348.12.2.rt7.143.el8_5
redhat/kernel<0:4.18.0-348.12.2.el8_5
0:4.18.0-348.12.2.el8_5
redhat/kernel<0:4.18.0-147.59.1.el8_1
0:4.18.0-147.59.1.el8_1
redhat/kernel-rt<0:4.18.0-193.75.1.rt13.125.el8_2
0:4.18.0-193.75.1.rt13.125.el8_2
redhat/kernel<0:4.18.0-193.75.1.el8_2
0:4.18.0-193.75.1.el8_2
redhat/kernel-rt<0:4.18.0-305.34.2.rt7.107.el8_4
0:4.18.0-305.34.2.rt7.107.el8_4
redhat/kernel<0:4.18.0-305.34.2.el8_4
0:4.18.0-305.34.2.el8_4
redhat/redhat-virtualization-host<0:4.3.22-20220330.1.el7_9
0:4.3.22-20220330.1.el7_9
Linux Linux kernel<5.16
redhat/Kernel<5.16
5.16
debian/linux
5.10.223-15.10.249-16.1.159-16.1.162-16.12.63-16.12.73-16.18.12-1

Remediation

Recommended actions to resolve this vulnerability, in priority order.

  1. Upgrade

    Upgrade redhat/kernel to a version that resolves this vulnerability.

    Fixed in 0:2.6.32-754.47.1.el6
  2. Upgrade

    Upgrade redhat/kernel-rt to a version that resolves this vulnerability.

    Fixed in 0:3.10.0-1160.59.1.rt56.1200.el7
  3. Upgrade

    Upgrade redhat/kernel to a version that resolves this vulnerability.

    Fixed in 0:3.10.0-1160.59.1.el7
  4. Upgrade

    Upgrade redhat/kernel to a version that resolves this vulnerability.

    Fixed in 0:3.10.0-514.97.1.el7
  5. Upgrade

    Upgrade redhat/kernel to a version that resolves this vulnerability.

    Fixed in 0:3.10.0-693.96.1.el7
  6. Upgrade

    Upgrade redhat/kernel to a version that resolves this vulnerability.

    Fixed in 0:3.10.0-957.88.1.el7
  7. Upgrade

    Upgrade redhat/kernel to a version that resolves this vulnerability.

    Fixed in 0:3.10.0-1062.63.1.el7
  8. Upgrade

    Upgrade redhat/kernel-rt to a version that resolves this vulnerability.

    Fixed in 0:4.18.0-348.12.2.rt7.143.el8_5
  9. Upgrade

    Upgrade redhat/kernel to a version that resolves this vulnerability.

    Fixed in 0:4.18.0-348.12.2.el8_5
  10. Upgrade

    Upgrade redhat/kernel to a version that resolves this vulnerability.

    Fixed in 0:4.18.0-147.59.1.el8_1
  11. Upgrade

    Upgrade redhat/kernel-rt to a version that resolves this vulnerability.

    Fixed in 0:4.18.0-193.75.1.rt13.125.el8_2
  12. Upgrade

    Upgrade redhat/kernel to a version that resolves this vulnerability.

    Fixed in 0:4.18.0-193.75.1.el8_2
  13. Upgrade

    Upgrade redhat/kernel-rt to a version that resolves this vulnerability.

    Fixed in 0:4.18.0-305.34.2.rt7.107.el8_4
  14. Upgrade

    Upgrade redhat/kernel to a version that resolves this vulnerability.

    Fixed in 0:4.18.0-305.34.2.el8_4
  15. Upgrade

    Upgrade redhat/redhat-virtualization-host to a version that resolves this vulnerability.

    Fixed in 0:4.3.22-20220330.1.el7_9
  16. Upgrade

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

    Fixed in 5.10.223-1Fixed in 5.10.249-1Fixed in 6.1.159-1Fixed in 6.1.162-1Fixed in 6.12.63-1Fixed in 6.12.73-1Fixed in 6.18.12-1
  17. Upgrade

    Upgrade redhat/Kernel to a version that resolves this vulnerability.

    Fixed in 5.16
  18. Compensating control

    Deploy the SystemTap mitigation for XFS by saving the CVE-2021-4155.stp script, ensuring xfs_alloc_file_space is not called with 0 as an argument, and resetting 0 with XFS_BMAPI_PREALLOC. Use $alloc_type = 0x40 for Red Hat Enterprise Linux 6 and $alloc_type = 0x8 for Red Hat Enterprise Linux 7 onwards.

  19. Operational

    Install the required packages with `yum install -y kernel-devel kernel-debuginfo` and `yum install -y systemtap systemtap-runtime`, then build the mitigation kernel module as root with `stap -r \`uname -r\` -m cve_2021_4155.ko -g CVE-2021-4155.stp -p4` and load it as root with `staprun -L cve_2021_4155.ko`.

Event History

Dec 22, 2021
Data Sourced
via Red Hat·08:55 AM
DescriptionSeverityAffected Software
Jan 10, 2022
CVE Published
06:36 AM
Aug 24, 2022
CVE Published
via MITRE·03:10 PM
Data Sourced
via MITRE·03:10 PM
DescriptionWeakness
Jan 12, 2024
Data Sourced
via Launchpad·12:01 AM
Description
May 2, 2025
Data Sourced
via Ubuntu·04:35 AM
RemedyDescriptionSeverityAffected Software
Feb 24, 2026
Data Sourced
via Debian·10:50 PM
DescriptionAffected Software

Parent advisories

This vulnerability appears in the following advisories.

Frequently Asked Questions

1

What is the severity of CVE-2021-4155?

CVE-2021-4155 is classified as a medium severity vulnerability due to its data leak implications.

2

How do I fix CVE-2021-4155?

To fix CVE-2021-4155, update your system to the appropriate kernel versions or apply available patches.

3

Who is affected by CVE-2021-4155?

CVE-2021-4155 affects local users with access to systems running specific versions of the XFS filesystem.

4

What type of vulnerability is CVE-2021-4155?

CVE-2021-4155 is a data leak vulnerability that allows unauthorized access to potentially sensitive information.

5

Can CVE-2021-4155 be exploited remotely?

No, CVE-2021-4155 requires local access, making it less likely to be exploited remotely.

Company

Resources

Contact

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