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Fencer Vulns
high 7.8

CVE-2021-26930 json

An issue was discovered in the Linux kernel 3.11 through 5.10.16, as used by Xen.

published 2021-02-17 5 y ago modified 2026-06-17 4 mo ago also EUVD-2021-13712

cvss
7.8
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
0.3%
EPSS 0.3% chance of exploitation in 30 days, percentile 28%
public exploits
0
none known

Summary

An issue was discovered in the Linux kernel 3.11 through 5.10.16, as used by Xen. To service requests to the PV backend, the driver maps grant references provided by the frontend. In this process, errors may be encountered. In one case, an error encountered earlier might be discarded by later processing, resulting in the caller assuming successful mapping, and hence subsequent operations trying to access space that wasn't mapped. In another case, internal state would be insufficiently updated, preventing safe recovery from the error. This affects drivers/block/xen-blkback/blkback.c.

Patch / fix

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

debian advisories DEBIAN-CVE-2021-26930

  • 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-2021-26930

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

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-2021-26930 updated cvss 7.8

xen: Linux: error handling issues in blkback's grant mapping

  • 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

0.35% chance of exploitation in the next 30 days, higher than 28% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
NVD 3.1 7.8 CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
NVD 2.0 4.6 AV:L/AC:L/Au:N/C:P/I:P/A:P

Classification

Technology feeds

References

Sources

Fencer Vulns 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.