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Fencer Vulns
medium 6.5

CVE-2021-3671 json

A null pointer de-reference was found in the way samba kerberos server handled missing sname in TGS-REQ (Ticket Granting Server - Request).

published 2021-10-12 5 y ago modified 2026-06-17 4 mo ago also EUVD-2021-26963

cvss
6.5
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
2.1%
EPSS 2.1% chance of exploitation in 30 days, percentile 81%
public exploits
0
none known

Summary

A null pointer de-reference was found in the way samba kerberos server handled missing sname in TGS-REQ (Ticket Granting Server - Request). An authenticated user could use this flaw to crash the samba server.

Patch / fix

  • samba samba 4.13.12, 4.14.8
  • samba Debian 14, Debian 13, Debian 12 2:4.13.13+dfsg-1
  • heimdal Debian 14, Debian 13, Debian 12 7.7.0+dfsg-3

debian advisories DEBIAN-CVE-2021-3671

  • samba Ubuntu 18.04 LTS 2:4.7.6+dfsg~ubuntu-0ubuntu2.26
  • samba Ubuntu 20.04 LTS 2:4.13.14+dfsg-0ubuntu0.20.04.1
  • samba Ubuntu 22.04 LTS 2:4.13.14+dfsg-0ubuntu1
  • heimdal Ubuntu 18.04 LTS 7.5.0+dfsg-1ubuntu0.1
  • heimdal Ubuntu 20.04 LTS 7.7.0+dfsg-1ubuntu1.1
  • heimdal Ubuntu Pro 14.04 LTS 1.6~git20131207+dfsg-1ubuntu1.2+esm1
  • heimdal Ubuntu Pro 16.04 LTS 1.7~git20150920+dfsg-4ubuntu1.16.04.1+esm1

ubuntu advisories UBUNTU-CVE-2021-3671

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

  • libheimdal Package Hub 15 SP3, openSUSE Leap 15.3 7.8.0-bp153.2.4.1
  • libheimdal Package Hub 15 SP4, openSUSE Leap 15.4 7.8.0-bp154.2.4.1

opensuse advisories openSUSE-SU-2023:0020-1openSUSE-SU-2023:0019-1

  • samba Alpine 3.14 4.14.8-r0
  • samba Alpine 3.24, Alpine 3.23, Alpine 3.22 +7 more 4.15.0-r0
  • heimdal Alpine 3.24, Alpine 3.23, Alpine 3.22 +8 more 7.7.1-r0

alpine advisories ALPINE-CVE-2021-3671

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-37004

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

  • samba Arch Linux 4.15.0-1

arch linux advisories AVG-2418

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-2021-3671 updated cvss 6.5

samba: Null pointer dereference on missing sname in TGS-REQ

  • Red Hat Enterprise Linux 7 ctdb, samba, samba-dc, ctdb-tests, samba-libs, samba-pidl, +18 more Red Hat Enterprise Linux 8 ctdb, samba, libnetapi, ctdb-tests, samba-libs, samba-pidl, +24 more Red Hat Enterprise Linux 9 ctdb, samba, libldb, ldb-tools, libnetapi, samba-libs, +27 more Red Hat Storage 3 ctdb, samba, samba-dc, ctdb-tests, samba-libs, samba-pidl, +21 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

2.12% chance of exploitation in the next 30 days, higher than 81% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
NVD 3.1 6.5 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
NVD 2.0 4.0 AV:N/AC:L/Au:S/C:N/I:N/A:P

Affected products

  • n/a Samba

Classification

Weakness

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.