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Fencer Vulns
high 7.8

CVE-2021-47343 json

dm btree remove: assign new_root only when removal succeeds

published 2024-05-21 2 y ago modified 2026-08-05 3 mo ago also EUVD-2021-34348

cvss
7.8
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.3%
EPSS 0.3% chance of exploitation in 30 days, percentile 19%
public exploits
0
none known

Summary

In the Linux kernel, the following vulnerability has been resolved:

dm btree remove: assign new_root only when removal succeeds

remove_raw() in dm_btree_remove() may fail due to IO read error (e.g. read the content of origin block fails during shadowing), and the value of shadow_spine::root is uninitialized, but the uninitialized value is still assign to new_root in the end of dm_btree_remove().

For dm-thin, the value of pmd->details_root or pmd->root will become an uninitialized value, so if trying to read details_info tree again out-of-bound memory may occur as showed below:

general protection fault, probably for non-canonical address 0x3fdcb14c8d7520 CPU: 4 PID: 515 Comm: dmsetup Not tainted 5.13.0-rc6 Hardware name: QEMU Standard PC RIP: 0010:metadata_ll_load_ie+0x14/0x30 Call Trace: sm_metadata_count_is_more_than_one+0xb9/0xe0 dm_tm_shadow_block+0x52/0x1c0 shadow_step+0x59/0xf0 remove_raw+0xb2/0x170 dm_btree_remove+0xf4/0x1c0 dm_pool_delete_thin_device+0xc3/0x140 pool_message+0x218/0x2b0 target_message+0x251/0x290 ctl_ioctl+0x1c4/0x4d0 dm_ctl_ioctl+0xe/0x20 __x64_sys_ioctl+0x7b/0xb0 do_syscall_64+0x40/0xb0 entry_SYSCALL_64_after_hwframe+0x44/0xae

Fixing it by only assign new_root when removal succeeds

Patch / fix

  • Linux Linux 4.4.276, 4.9.276, 4.14.240, 4.19.198, 5.4.133, 5.10.51, 5.12.18, 5.13.3, 5.14
  • linux Debian 14, Debian 13, Debian 12 5.14.6-1

debian advisories DEBIAN-CVE-2021-47343

  • linux Ubuntu 18.04 LTS 4.15.0-156.163
  • linux Ubuntu 20.04 LTS 5.4.0-84.94
  • linux-aws Ubuntu 18.04 LTS 4.15.0-1111.118
  • linux-aws Ubuntu 20.04 LTS 5.4.0-1056.59
  • linux-gcp Ubuntu 20.04 LTS 5.4.0-1052.56
  • linux-kvm Ubuntu 18.04 LTS 4.15.0-1099.101
  • linux-kvm Ubuntu 20.04 LTS 5.4.0-1046.48
  • linux-azure Ubuntu 20.04 LTS 5.4.0-1058.60

ubuntu advisories UBUNTU-CVE-2021-47343

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-64kb SLES 15 SP3-LTSS, SLE High Performance Computing 15 SP3-LTSS, Enterprise Storage 7.1 5.3.18-150300.59.164.1
  • kernel-syms SLES for SAP 15 SP3, SLES 15 SP3-LTSS, SLE High Performance Computing 15 SP3-LTSS +1 more 5.3.18-150300.59.164.1
  • kernel-source SLES for SAP 15 SP3, SLES 15 SP3-LTSS, SLE High Performance Computing 15 SP3-LTSS +1 more 5.3.18-150300.59.164.1
  • kernel-default SLES for SAP 15 SP3, SLES 15 SP3-LTSS, SLE Micro 5.2 +5 more 5.3.18-150300.59.164.1
  • kernel-preempt SLES for SAP 15 SP3, SLES 15 SP3-LTSS, SLE High Performance Computing 15 SP3-LTSS +1 more 5.3.18-150300.59.164.1
  • kernel-obs-build SLES for SAP 15 SP3, SLES 15 SP3-LTSS, SLE High Performance Computing 15 SP3-LTSS +1 more 5.3.18-150300.59.164.1
  • kernel-default-base SLES for SAP 15 SP3, SLES 15 SP3-LTSS, SLE Micro 5.2 +3 more 5.3.18-150300.59.164.1.150300.18.96.1
  • kernel-syms SLES for SAP 12 SP5, SLES 12 SP5 4.12.14-122.219.1

suse advisories SUSE-SU-2024:2185-1SUSE-SU-2024:2184-1SUSE-SU-2024:2010-1SUSE-SU-2024:1983-1SUSE-SU-2024:1979-1

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-2021-47343 updated cvss 4.4

kernel: dm btree remove: assign new_root only when removal succeeds

  • Red Hat Enterprise Linux 6 perf, kernel, python-perf, kernel-kdump, kernel-firmware, kernel-bootwrapper, +1 more Red Hat Enterprise Linux 7 perf, kernel, bpftool, kernel-rt, python-perf, kernel-kdump, +8 more
    affected: workaround, no fix planned “Red Hat has investigated whether a possible mitigation exists for this issue, and has not been able to identify a practical example. Please update the affected package as soon as possible.”
  • Red Hat Enterprise Linux 8 perf, kernel, bpftool, kernel-rt, kernel-core, kernel-tools, +29 more Red Hat Enterprise Linux 9 kernel-rt, kernel-rt-selftests-internal
    affected: workaround, no fix available “Red Hat has investigated whether a possible mitigation exists for this issue, and has not been able to identify a practical example. Please update the affected package as soon as possible.”
  • Red Hat Enterprise Linux 9 rv, perf, rtla, kernel, bpftool, libperf, +82 more
    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

CISA SSVC

Exploitation
none
Automatable
no
Technical impact
partial
Assessed
2 y ago

Exploit prediction

0.27% chance of exploitation in the next 30 days, higher than 19% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 7.8 CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
NVD 3.1 5.5 CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Affected products

  • Linux Linux

Classification

Weakness
  • CWE-1188 Initialization of a Resource with an Insecure Default
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.