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Fencer Vulns
low 2.5

CVE-2021-43566 json

All versions of Samba prior to 4.13.16 are vulnerable to a malicious client using an SMB1 or NFS race to allow a directory to be created in…

published 2022-01-11 4 y ago modified 2026-06-17 4 mo ago also EUVD-2021-30489

cvss
2.5
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
0.4%
EPSS 0.4% chance of exploitation in 30 days, percentile 34%
public exploits
0
none known

Summary

All versions of Samba prior to 4.13.16 are vulnerable to a malicious client using an SMB1 or NFS race to allow a directory to be created in an area of the server file system not exported under the share definition. Note that SMB1 has to be enabled, or the share also available via NFS in order for this attack to succeed.

Patch / fix

  • samba samba 4.13.16
  • samba Debian 14, Debian 13, Debian 12 2:4.16.0+dfsg-2

debian advisories DEBIAN-CVE-2021-43566

  • samba Ubuntu 20.04 LTS 2:4.13.17~dfsg-0ubuntu0.21.04.1

ubuntu advisories UBUNTU-CVE-2021-43566

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

  • samba RHEL 8 4.14.5-2.el8
  • ctdb RHEL 8 4.14.5-2.el8
  • samba-libs RHEL 8 4.14.5-2.el8
  • samba-pidl RHEL 8 4.14.5-2.el8
  • samba-test RHEL 8 4.14.5-2.el8
  • libwbclient RHEL 8 4.14.5-2.el8
  • libsmbclient RHEL 8 4.14.5-2.el8
  • samba-client RHEL 8 4.14.5-2.el8

red hat advisories RHBA-2021:4438

  • samba SLES for SAP 12 SP5, SLES 12 SP5, SLE Software Development Kit 12 SP5 +1 more 4.15.4+git.324.8332acf1a63-3.54.1
  • sssd SLES for SAP 12 SP5, SLES 12 SP5, SLE Software Development Kit 12 SP5 1.16.1-7.28.9
  • gnutls SLES for SAP 12 SP5, SLES 12 SP5 3.4.17-8.4.1
  • p11-kit SLES for SAP 12 SP5, SLES 12 SP5, SLE Software Development Kit 12 SP5 0.23.2-8.3.2
  • apparmor SLES for SAP 12 SP5, SLES 12 SP5, SLE Software Development Kit 12 SP5 2.8.2-56.6.3
  • libnettle SLES for SAP 12 SP5, SLES 12 SP5 3.1-21.3.2
  • ca-certificates SLES for SAP 12 SP5, SLES 12 SP5 1_201403302107-15.3.3
  • yast2-samba-client SLES for SAP 12 SP5, SLES 12 SP5 3.1.23-3.3.1

suse advisories SUSE-SU-2022:0323-1SUSE-SU-2022:0283-1

  • samba openSUSE Leap 15.3 4.15.4+git.324.8332acf1a63-150300.3.25.3
  • ldb openSUSE Leap 15.3 2.4.1-150300.3.10.1
  • tdb openSUSE Leap 15.3 1.4.4-150300.3.3.2
  • krb5 openSUSE Leap 15.3 1.19.2-150300.8.3.2
  • sssd openSUSE Leap 15.3 1.16.1-150300.23.17.3
  • talloc openSUSE Leap 15.3 2.3.3-150300.3.3.2
  • tevent openSUSE Leap 15.3 0.11.0-150300.3.3.2
  • apparmor openSUSE Leap 15.3 2.13.6-150300.3.11.2

opensuse advisories openSUSE-SU-2022:0283-1

  • samba Alpine 3.13 4.13.17-r0

alpine advisories ALPINE-CVE-2021-43566

Alpine secdb © Alpine Linux, from https://secdb.alpinelinux.org via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • samba Azure Linux 3.0 4.18.3-1

azure linux advisories AZL-37006

Azure Linux vulnerability data, Copyright (c) Microsoft Corporation, from https://github.com/microsoft/AzureLinuxVulnerabilityData via OSV, under the MIT licence; changed: normalised to fixed package versions per release. MIT

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-2021-43566 updated cvss 2.6

samba: Symlink race error can allow directory creation outside of the exported share

  • Red Hat Enterprise Linux 6 samba, samba4, samba4-dc, samba-swat, samba4-libs, samba4-pidl, +17 more Red Hat Enterprise Linux 7 ctdb, samba, samba-dc, ctdb-tests, samba-libs, samba-pidl, +18 more
    affected: workaround, no fix planned “Out of support scope”
  • Red Hat Storage 3 ctdb, samba, samba-dc, ctdb-tests, samba-libs, samba-pidl, +21 more
    affected: workaround, no fix available
  • Red Hat CodeReady Linux Builder (v. 8) samba-devel 4.14.5-2.el8, ctdb-debuginfo 4.14.5-2.el8, samba-debuginfo 4.14.5-2.el8, libwbclient-devel 4.14.5-2.el8, samba-debugsource 4.14.5-2.el8, libsmbclient-devel 4.14.5-2.el8, +17 more Red Hat Enterprise Linux AppStream (v. 8) samba-vfs-iouring 4.14.5-2.el8 Red Hat Enterprise Linux BaseOS (v. 8) ctdb 4.14.5-2.el8, samba 4.14.5-2.el8, samba-libs 4.14.5-2.el8, samba-pidl 4.14.5-2.el8, samba-test 4.14.5-2.el8, libwbclient 4.14.5-2.el8, +15 more
    fixed: vendor fix RHBA-2021:4438
  • Red Hat Enterprise Linux 9 ctdb, samba, libldb, ldb-tools, libnetapi, samba-libs, +27 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

Exploit prediction

0.40% chance of exploitation in the next 30 days, higher than 34% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • bugzilla.samba.org https://bugzilla.samba.org/show_bug.cgi?id=13979 referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
NVD 3.1 2.5 CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:L/A:N
NVD 2.0 1.2 AV:L/AC:H/Au:N/C:N/I:P/A:N

Classification

Weakness
  • CWE-362 Concurrent Execution using Shared Resource with Improper Synchronization

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.