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Fencer Intel
medium 5.5

CVE-2021-26931 json

An issue was discovered in the Linux kernel 2.6.39 through 5.10.16, as used in Xen.

published 5y ago modified 4mo ago also EUVD-2021-13713

cvss
5.5
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
0.6%
EPSS 0.6% chance of exploitation in 30 days, percentile 46%
public exploits
0
none known

Summary

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.

Patch / fix

  • linux Debian 14, Debian 13, Debian 12 5.10.19-1

debian advisories DEBIAN-CVE-2021-26931

  • linux Ubuntu 16.04 LTS 4.4.0-208.240
  • linux Ubuntu 18.04 LTS 4.15.0-143.147
  • linux Ubuntu 20.04 LTS 5.4.0-71.79
  • linux-aws Ubuntu 16.04 LTS 4.4.0-1126.140
  • linux-aws Ubuntu 18.04 LTS 4.15.0-1102.109
  • linux-aws Ubuntu 20.04 LTS 5.4.0-1043.45
  • linux-gcp Ubuntu 20.04 LTS 5.4.0-1041.44
  • linux-gke Ubuntu 20.04 LTS 5.4.0-1041.43

ubuntu advisories UBUNTU-CVE-2021-26931

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • kernel-syms SLES for SAP 12 SP5, SLES 12 SP5 4.12.14-122.66.2
  • kernel-source SLES for SAP 12 SP5, SLES 12 SP5 4.12.14-122.66.2
  • kernel-default SLES for SAP 12 SP5, SLES 12 SP5, SLE Workstation Extension 12 SP5 +2 more 4.12.14-122.66.2
  • kernel-obs-build SLE Software Development Kit 12 SP5 4.12.14-122.66.2
  • kernel-rt SLE Real Time 12 SP5 4.12.14-10.37.1
  • kernel-syms-rt SLE Real Time 12 SP5 4.12.14-10.37.1
  • kernel-rt_debug SLE Real Time 12 SP5 4.12.14-10.37.1
  • kernel-source-rt SLE Real Time 12 SP5 4.12.14-10.37.1

suse advisories SUSE-SU-2021:1365-1SUSE-SU-2021:1344-1SUSE-SU-2021:1373-1SUSE-SU-2021:1210-1SUSE-SU-2021:1176-1SUSE-SU-2021:1175-1

  • kernel-syms openSUSE Leap 15.2 5.3.18-lp152.66.2
  • kernel-obs-qa openSUSE Leap 15.2 5.3.18-lp152.66.2
  • kernel-source openSUSE Leap 15.2 5.3.18-lp152.66.2
  • kernel-default openSUSE Leap 15.2 5.3.18-lp152.66.2
  • kernel-preempt openSUSE Leap 15.2 5.3.18-lp152.66.2
  • kernel-kvmsmall openSUSE Leap 15.2 5.3.18-lp152.66.2
  • kernel-obs-build openSUSE Leap 15.2 5.3.18-lp152.66.2
  • kernel-default-base openSUSE Leap 15.2 5.3.18-lp152.66.2.lp152.8.23.2

opensuse advisories openSUSE-SU-2021:0393-1

  • linux Arch Linux 5.11.1.arch1-1
  • linux-hardened Arch Linux 5.10.18.hardened1-1
  • linux-zen Arch Linux 5.11.1.zen1-1
  • linux-lts Arch Linux 5.10.18-1

arch linux advisories AVG-1580AVG-1613AVG-1614AVG-1615

Is CVE-2021-26931 in your stack? Fencer shows which of your repositories are affected as soon as an advisory lands, and opens the fix as a pull request.

Check with Fencer

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2021-26931 updated cvss 6.5

xen: Linux: backends treating grant mapping errors as bugs

  • Red Hat All currently supported Red Hat products
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

Exploit prediction

0.56% chance of exploitation in the next 30 days, higher than 46% of all scored CVEs (FIRST EPSS, 2026-11-09).

CVSS scores

assigned by version score vector
NVD 3.1 5.5 CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
NVD 2.0 1.9 AV:L/AC:M/Au:N/C:N/I:N/A:P

Classification

Weakness
  • CWE-770 Allocation of Resources Without Limits or Throttling
Technology feeds

References

Sources

Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.