RHSA-2021:5192HighCVSS 8.1

Red Hat Security Advisory: samba security and bug fix update

Published
December 16, 2021
Last Modified
November 5, 2026

🔗 CVE IDs covered (2)

CVE-2016-2124 →CVE-2020-25717 →

📋 Description

CVE-2016-2124 — samba: SMB1 client connections can be downgraded to plaintext authentication CVE-2020-25717 — samba: Active Directory (AD) domain user could become root on domain members

🎯 Affected products200

  • Red Hat Enterprise Linux Client (v. 7)
  • Red Hat Enterprise Linux Client Optional (v. 7)
  • Red Hat Enterprise Linux ComputeNode Optional (v. 7)
  • Red Hat Enterprise Linux Server (v. 7)
  • Red Hat Enterprise Linux Server Optional (v. 7)
  • Red Hat Enterprise Linux Server Resilient Storage (v. 7)
  • Red Hat Enterprise Linux Workstation (v. 7)
  • Red Hat Enterprise Linux Workstation Optional (v. 7)
  • ctdb-0:4.10.16-17.el7_9.ppc64le as a component of Red Hat Enterprise Linux Server Resilient Storage (v. 7)
  • ctdb-0:4.10.16-17.el7_9.s390x as a component of Red Hat Enterprise Linux Server Resilient Storage (v. 7)
  • ctdb-0:4.10.16-17.el7_9.x86_64 as a component of Red Hat Enterprise Linux Server Resilient Storage (v. 7)
  • ctdb-tests-0:4.10.16-17.el7_9.ppc64le as a component of Red Hat Enterprise Linux Server Resilient Storage (v. 7)
  • ctdb-tests-0:4.10.16-17.el7_9.s390x as a component of Red Hat Enterprise Linux Server Resilient Storage (v. 7)
  • ctdb-tests-0:4.10.16-17.el7_9.x86_64 as a component of Red Hat Enterprise Linux Server Resilient Storage (v. 7)
  • libsmbclient-0:4.10.16-17.el7_9.i686 as a component of Red Hat Enterprise Linux Client (v. 7)
  • libsmbclient-0:4.10.16-17.el7_9.i686 as a component of Red Hat Enterprise Linux Server (v. 7)
  • libsmbclient-0:4.10.16-17.el7_9.i686 as a component of Red Hat Enterprise Linux Workstation (v. 7)
  • libsmbclient-0:4.10.16-17.el7_9.ppc as a component of Red Hat Enterprise Linux Server (v. 7)
  • libsmbclient-0:4.10.16-17.el7_9.ppc64 as a component of Red Hat Enterprise Linux Server (v. 7)
  • libsmbclient-0:4.10.16-17.el7_9.ppc64le as a component of Red Hat Enterprise Linux Server (v. 7)
  • libsmbclient-0:4.10.16-17.el7_9.s390 as a component of Red Hat Enterprise Linux Server (v. 7)
  • libsmbclient-0:4.10.16-17.el7_9.s390x as a component of Red Hat Enterprise Linux Server (v. 7)
  • libsmbclient-0:4.10.16-17.el7_9.x86_64 as a component of Red Hat Enterprise Linux Client (v. 7)
  • libsmbclient-0:4.10.16-17.el7_9.x86_64 as a component of Red Hat Enterprise Linux Server (v. 7)
  • libsmbclient-0:4.10.16-17.el7_9.x86_64 as a component of Red Hat Enterprise Linux Workstation (v. 7)
  • libsmbclient-devel-0:4.10.16-17.el7_9.i686 as a component of Red Hat Enterprise Linux Client Optional (v. 7)
  • libsmbclient-devel-0:4.10.16-17.el7_9.i686 as a component of Red Hat Enterprise Linux ComputeNode Optional (v. 7)
  • libsmbclient-devel-0:4.10.16-17.el7_9.i686 as a component of Red Hat Enterprise Linux Server Optional (v. 7)
  • libsmbclient-devel-0:4.10.16-17.el7_9.i686 as a component of Red Hat Enterprise Linux Workstation Optional (v. 7)
  • libsmbclient-devel-0:4.10.16-17.el7_9.ppc as a component of Red Hat Enterprise Linux Server Optional (v. 7)
  • +170 more not shown

✅ Remediation

For details on how to apply this update, which includes the changes described in this advisory, refer to: https://access.redhat.com/articles/11258 After installing this update, the smb service will be restarted automatically. Workaround: Ensure the following [global] smb.conf parameters are set to their default values as shown below: ~~~ client lanman auth = no client NTLMv2 auth = yes client plaintext auth = no client min protocol = SMB2_02 ~~~ Or use the '-k' command line option only without the -U option, which will make use of an existing krb5 ccache. Workaround: Setting "gensec:require_pac=true" in the smb.conf makes, due to a cache prime in winbind, the DOMAIN\user lookup succeed, provided nss_winbind is in use, 'winbind use default domain = no' (the default) and no error paths are hit. It would be prudent to pre-create disabled users in Active Directory matching on all privileged names not held in Active Directory, eg ~~~ samba-tool user add root -H ldap://$SERVER -U$USERNAME%$PASSWORD --random-password samba-tool user add ubuntu -H ldap://$SERVER -U$USERNAME%$PASSWORD --random-password ~~~ (repeat for eg all system users under 1000 in /etc/passwd or special to any other AD-connected services, eg perhaps "admin" for a web-app)

🔗 References (5)