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UBUNTU-CVE-2021-26931 Moderate

UBUNTU-CVE-2021-26931

An issue was discovered in the Linux kernel 2.6.39 through 5.10.16, as used in Xen. Block, net, and SCSI backends consider certain errors a plain bug, deliberately causing a kernel crash. For errors potentially being at least under the influence of guests (such as out of memory conditions), it isn't correct to assume a plain bug. Memory allocations potentially causing such crashes occur only when Linux is running in PV mode, though. This affects drivers/block/xen-blkback/blkback.c and drivers/xen/xen-scsiback.c.

Exploit probability Not scored
Published February 17, 2021
Required by Not available
Last source change August 18, 2026

02 / AFFECTED SOFTWARE

Affected packages

Ubuntu:18.04:LTS linux-oem

50 explicit affected versions

Ubuntu:18.04:LTS linux-aws-5.0

6 explicit affected versions

Ubuntu:20.04:LTS linux-raspi2

6 explicit affected versions

Ubuntu:Pro:20.04:LTS linux-azure-fde-5.15

57 explicit affected versions

Ubuntu:Pro:14.04:LTS linux

191 explicit affected versions

Ubuntu:18.04:LTS linux-aws

64 explicit affected versions

Ubuntu:20.04:LTS linux-kvm

23 explicit affected versions

Ubuntu:18.04:LTS linux-oracle

44 explicit affected versions

Ubuntu:Pro:FIPS-updates:18.04:LTS linux-azure-fips

17 explicit affected versions

Ubuntu:18.04:LTS linux

74 explicit affected versions

Ubuntu:16.04:LTS linux-hwe-edge

23 explicit affected versions

Ubuntu:Pro:FIPS:18.04:LTS linux-gcp-fips

1 explicit affected versions

Ubuntu:24.04:LTS linux-raspi-realtime

1 explicit affected versions

Ubuntu:20.04:LTS linux-hwe-5.8

17 explicit affected versions

Ubuntu:Pro:FIPS-updates:20.04:LTS linux-aws-fips

1 explicit affected versions

Ubuntu:18.04:LTS linux-oracle-5.0

7 explicit affected versions

Ubuntu:20.04:LTS linux-riscv

12 explicit affected versions

Ubuntu:22.04:LTS linux-intel-iot-realtime

1 explicit affected versions

Ubuntu:20.04:LTS linux-gcp

25 explicit affected versions

Ubuntu:20.04:LTS linux

33 explicit affected versions

Ubuntu:16.04:LTS linux-kvm

60 explicit affected versions

Ubuntu:20.04:LTS linux-azure

24 explicit affected versions

Ubuntu:18.04:LTS linux-gcp-4.15

19 explicit affected versions

Ubuntu:18.04:LTS linux-hwe-edge

10 explicit affected versions

Ubuntu:18.04:LTS linux-gke-5.4

10 explicit affected versions

Ubuntu:Pro:14.04:LTS linux-aws

59 explicit affected versions

Ubuntu:18.04:LTS linux-snapdragon

41 explicit affected versions

Ubuntu:Pro:FIPS:20.04:LTS linux-aws-fips

1 explicit affected versions

Ubuntu:20.04:LTS linux-oem-5.10

5 explicit affected versions

Ubuntu:Pro:FIPS:18.04:LTS linux-fips

1 explicit affected versions

Ubuntu:20.04:LTS linux-oem-5.6

29 explicit affected versions

Ubuntu:18.04:LTS linux-gcp-5.3

13 explicit affected versions

Ubuntu:18.04:LTS linux-kvm

58 explicit affected versions

Ubuntu:Pro:FIPS:18.04:LTS linux-azure-fips

1 explicit affected versions

Ubuntu:20.04:LTS linux-aws

27 explicit affected versions

Ubuntu:18.04:LTS linux-gke-4.15

33 explicit affected versions

Ubuntu:18.04:LTS linux-aws-5.3

10 explicit affected versions

Ubuntu:Pro:16.04:LTS linux-aws-hwe

43 explicit affected versions

Ubuntu:Nvidia-BlueField:24.04:LTS linux-bluefield

11 explicit affected versions

Ubuntu:16.04:LTS linux-raspi2

94 explicit affected versions

Ubuntu:Pro:16.04:LTS linux-gcp

66 explicit affected versions

Ubuntu:20.04:LTS linux-oracle

25 explicit affected versions

Ubuntu:Pro:FIPS:16.04:LTS linux-fips

2 explicit affected versions

Ubuntu:18.04:LTS linux-raspi2

61 explicit affected versions

Ubuntu:18.04:LTS linux-hwe-5.4

21 explicit affected versions

Ubuntu:Pro:FIPS:20.04:LTS linux-azure-fips

1 explicit affected versions

Ubuntu:16.04:LTS linux

125 explicit affected versions

Ubuntu:20.04:LTS linux-gke

5 explicit affected versions

Ubuntu:18.04:LTS linux-azure-4.15

20 explicit affected versions

Ubuntu:Pro:FIPS:18.04:LTS linux-aws-fips

1 explicit affected versions

Ubuntu:Pro:FIPS-updates:18.04:LTS linux-fips

23 explicit affected versions

Ubuntu:18.04:LTS linux-gcp-5.4

15 explicit affected versions

Ubuntu:Pro:FIPS:20.04:LTS linux-gcp-fips

1 explicit affected versions

Ubuntu:18.04:LTS linux-aws-5.4

15 explicit affected versions

Ubuntu:Pro:FIPS-updates:20.04:LTS linux-azure-fips

1 explicit affected versions

Ubuntu:Pro:FIPS-updates:18.04:LTS linux-aws-fips

20 explicit affected versions

Ubuntu:20.04:LTS linux-riscv-5.8

7 explicit affected versions

Ubuntu:16.04:LTS linux-aws

81 explicit affected versions

Ubuntu:18.04:LTS linux-raspi-5.4

14 explicit affected versions

Ubuntu:18.04:LTS linux-azure

44 explicit affected versions

Ubuntu:18.04:LTS linux-azure-5.3

16 explicit affected versions

Ubuntu:18.04:LTS linux-gkeop-5.4

10 explicit affected versions

Ubuntu:18.04:LTS linux-gcp

38 explicit affected versions

Ubuntu:18.04:LTS linux-oracle-5.3

9 explicit affected versions

Ubuntu:Pro:14.04:LTS linux-lts-xenial

103 explicit affected versions

Ubuntu:18.04:LTS linux-oracle-5.4

15 explicit affected versions

Ubuntu:Pro:FIPS:16.04:LTS linux-fips

38 explicit affected versions

Ubuntu:Pro:16.04:LTS linux-azure

74 explicit affected versions

Ubuntu:Pro:14.04:LTS linux-azure

51 explicit affected versions

Ubuntu:18.04:LTS linux-dell300x

11 explicit affected versions

Ubuntu:Pro:16.04:LTS linux-oracle

42 explicit affected versions

Ubuntu:18.04:LTS linux-azure-5.4

14 explicit affected versions

Ubuntu:18.04:LTS linux-hwe

43 explicit affected versions

Ubuntu:Pro:FIPS-updates:20.04:LTS linux-gcp-fips

1 explicit affected versions

Ubuntu:Pro:16.04:LTS linux-hwe

89 explicit affected versions

Ubuntu:18.04:LTS linux-gcp-edge

12 explicit affected versions

Ubuntu:20.04:LTS linux-raspi

18 explicit affected versions

Ubuntu:18.04:LTS linux-azure-edge

4 explicit affected versions

Ubuntu:20.04:LTS linux-gkeop

5 explicit affected versions

Ubuntu:22.04:LTS linux-realtime

1 explicit affected versions

Ubuntu:16.04:LTS linux-snapdragon

92 explicit affected versions

03 / CONNECTIONS

Connected vulnerabilities

04 / EVIDENCE

Source records

Open Source Vulnerabilities UBUNTU-CVE-2021-26931

An issue was discovered in the Linux kernel 2.6.39 through 5.10.16, as used in Xen. Block, net, and SCSI backends consider certain errors a plain bug, deliberately causing a kernel crash. For errors potentially being at least under the influence of guests (such as out of memory conditions), it isn't correct to assume a plain bug. Memory allocations potentially causing such crashes occur only when Linux is running in PV mode, though. This affects drivers/block/xen-blkback/blkback.c and drivers/xen/xen-scsiback.c.

View original source

05 / REFERENCES

Further evidence