CVE-2021-33909: Integer Overflow

Published Jun 10, 2021
·
Updated

An out-of-bounds write flaw was found in the Linux kernel's seqfile in the Filesystem layer. This flaw allows a local attacker with a user privilege to gain access to out-of-bound memory, leading to a system crash, leak of internal kernel information and can escalate privileges. The issue results from not validating the sizet-to-int conversion prior to performing operations. The highest threat from this vulnerability is to data integrity, confidentiality and system availability.

Other sources

An out-of-bounds write flaw was found in the seqfile in Filesystem layer, where a local attacker with a user privilege could gain access to out-of-bound memory leading to a system crash or a leak of internal kernel information. The issue results from not validating the sizet-to-int conversion prior to performing operations. The highest threat from this vulnerability is to data integrity, confidentiality and system availability.

While creating, mounting, and deleting a deep directory structure whose total path length exceeds 1GB, an unprivileged local attacker can write the 10-byte string "//deleted" to an offset of exactly -2GB-10B below the beginning of a vmalloc()ated kernel buffer.

References: https://www.openwall.com/lists/oss-security/2021/07/20/1 https://www.qualys.com/2021/07/20/cve-2021-33909/sequoia-local-privilege-escalation-linux.txt

Fix: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=8cae8cd89f05f6de223d63e6d15e31c8ba9cf53b

— Red Hat

fs/seqfile.c in the Linux kernel 3.16 through 5.13.x before 5.13.4 does not properly restrict seq buffer allocations, leading to an integer overflow, an Out-of-bounds Write, and escalation to root by an unprivileged user, aka CID-8cae8cd89f05.

Linux Kernel could allow a local attacker to gain elevated privileges on the system, caused by an out-of-bounds write in fs/seqfile.c. By sending a specially-crafted request, an attacker could exploit this vulnerability to escalate privileges to root.

— IBM

Affected Software

42 affected componentsFixes available
redhat/kernel<0:2.6.32-754.41.2.el6
0:2.6.32-754.41.2.el6
redhat/kernel-rt<0:3.10.0-1160.36.2.rt56.1179.el7
0:3.10.0-1160.36.2.rt56.1179.el7
redhat/kernel<0:3.10.0-1160.36.2.el7
0:3.10.0-1160.36.2.el7
redhat/kernel<0:3.10.0-327.98.2.el7
0:3.10.0-327.98.2.el7
redhat/kernel<0:3.10.0-514.90.2.el7
0:3.10.0-514.90.2.el7
redhat/kernel<0:3.10.0-693.90.2.el7
0:3.10.0-693.90.2.el7
redhat/kernel<0:3.10.0-957.78.2.el7
0:3.10.0-957.78.2.el7
redhat/kernel<0:3.10.0-1062.52.2.el7
0:3.10.0-1062.52.2.el7
redhat/kernel-rt<0:4.18.0-305.10.2.rt7.83.el8_4
0:4.18.0-305.10.2.rt7.83.el8_4
redhat/kernel<0:4.18.0-305.10.2.el8_4
0:4.18.0-305.10.2.el8_4
redhat/kernel<0:4.18.0-147.51.2.el8_1
0:4.18.0-147.51.2.el8_1
redhat/kernel-rt<0:4.18.0-193.60.2.rt13.112.el8_2
0:4.18.0-193.60.2.rt13.112.el8_2
redhat/kernel<0:4.18.0-193.60.2.el8_2
0:4.18.0-193.60.2.el8_2
redhat/redhat-virtualization-host<0:4.3.17-20210713.0.el7_9
0:4.3.17-20210713.0.el7_9
redhat/redhat-virtualization-host<0:4.4.7-20210715.1.el8_4
0:4.4.7-20210715.1.el8_4
IBM DRM<=2.0.6
Linux Linux kernel>=3.12.43<3.13
Linux Linux kernel>=3.16<4.4.276
Linux Linux kernel>=4.5<4.9.276
Linux Linux kernel>=4.10<4.14.240
Linux Linux kernel>=4.15<4.19.198
Linux Linux kernel>=4.20<5.4.134
Linux Linux kernel>=5.5<5.10.52
Linux Linux kernel>=5.11<5.12.19
Linux Linux kernel>=5.13<5.13.4
Fedoraproject Fedora=34
Debian Debian Linux=9.0
Debian Debian Linux=10.0
NetApp Hci Management Node
NetApp Solidfire
Oracle Communications Session Border Controller=8.2
Oracle Communications Session Border Controller=8.3
Oracle Communications Session Border Controller=8.4
Oracle Communications Session Border Controller=9.0
All of the following
SonicWall Sma1000 Firmware<=12.4.2-02044
SonicWall SMA1000
SonicWall Sma1000 Firmware<=12.4.2-02044
SonicWall SMA1000
debian/linux
5.10.223-15.10.234-16.1.129-16.1.135-16.12.25-1
redhat/kernel<5.14
5.14
Google Android
android/:linux_kernel:>=:0<:2021-12-05
:2021-12-05

Remediation

Recommended actions to resolve this vulnerability, in priority order.

  1. Upgrade

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

    Fixed in 0:2.6.32-754.41.2.el6
  2. Upgrade

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

    Fixed in 0:3.10.0-1160.36.2.rt56.1179.el7
  3. Upgrade

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

    Fixed in 0:3.10.0-1160.36.2.el7
  4. Upgrade

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

    Fixed in 0:3.10.0-327.98.2.el7
  5. Upgrade

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

    Fixed in 0:3.10.0-514.90.2.el7
  6. Upgrade

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

    Fixed in 0:3.10.0-693.90.2.el7
  7. Upgrade

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

    Fixed in 0:3.10.0-957.78.2.el7
  8. Upgrade

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

    Fixed in 0:3.10.0-1062.52.2.el7
  9. Upgrade

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

    Fixed in 0:4.18.0-305.10.2.rt7.83.el8_4
  10. Upgrade

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

    Fixed in 0:4.18.0-305.10.2.el8_4
  11. Upgrade

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

    Fixed in 0:4.18.0-147.51.2.el8_1
  12. Upgrade

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

    Fixed in 0:4.18.0-193.60.2.rt13.112.el8_2
  13. Upgrade

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

    Fixed in 0:4.18.0-193.60.2.el8_2
  14. Upgrade

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

    Fixed in 0:4.3.17-20210713.0.el7_9
  15. Upgrade

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

    Fixed in 0:4.4.7-20210715.1.el8_4
  16. Upgrade

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

    Fixed in 5.10.223-1Fixed in 5.10.234-1Fixed in 6.1.129-1Fixed in 6.1.135-1Fixed in 6.12.25-1
  17. Upgrade

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

    Fixed in 5.14
  18. Upgrade

    Upgrade android/:linux_kernel: to a version that resolves this vulnerability.

    Fixed in :2021-12-05
  19. Upgrade

    Upgrade Linux kernel to a version that resolves this vulnerability.

    Fixed in 5.13.4

Event History

Jun 10, 2021
Data Sourced
via Red Hat·08:17 AM
DescriptionSeverityAffected Software
Jul 20, 2021
CVE Published
12:00 PM
CVE Published
via MITRE·06:01 PM
Data Sourced
via MITRE·06:01 PM
Description
Jul 21, 2021
Exploit Published
via GitHub·04:04 AM
Dec 1, 2021
Advisory Published
via OSV·12:00 AM
Data Sourced
via OSV·12:00 AM
DescriptionAffected Software
Dec 6, 2021
Data Sourced
via Android·12:00 AM
SeverityWeaknessAffected Software

Parent advisories

This vulnerability appears in the following advisories.

Frequently Asked Questions

1

What is the severity of CVE-2021-33909?

CVE-2021-33909 is classified as a high severity vulnerability that allows local privilege escalation due to an out-of-bounds write flaw in the Linux kernel.

2

How do I fix CVE-2021-33909?

To mitigate CVE-2021-33909, users should update to the recommended kernel versions provided by their Linux distribution.

3

What impact does CVE-2021-33909 have on affected systems?

CVE-2021-33909 can lead to system crashes, leakage of internal kernel information, and privilege escalation for local attackers.

4

Is CVE-2021-33909 exploitable remotely?

CVE-2021-33909 is not exploitable remotely as it requires local user privileges to be exploited.

5

Which versions of Linux are affected by CVE-2021-33909?

CVE-2021-33909 affects various versions of the Linux kernel, specifically those prior to the patched versions listed by the respective distributions.

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