RHSA-2021:4843HighCVSS 8.1

Red Hat Security Advisory: samba security update

Published
November 29, 2021
Last Modified
November 5, 2026

🔗 CVE IDs covered (3)

CVE-2020-25717 →CVE-2021-23192 →CVE-2016-2124 →

📋 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 CVE-2021-23192 — samba: Subsequent DCE/RPC fragment injection vulnerability

🎯 Affected products44

  • Red Hat Gluster 3.5 Samba on RHEL-8
  • ctdb-0:4.14.5-204.el8rhgs.x86_64 as a component of Red Hat Gluster 3.5 Samba on RHEL-8
  • ctdb-debuginfo-0:4.14.5-204.el8rhgs.x86_64 as a component of Red Hat Gluster 3.5 Samba on RHEL-8
  • libsmbclient-0:4.14.5-204.el8rhgs.x86_64 as a component of Red Hat Gluster 3.5 Samba on RHEL-8
  • libsmbclient-debuginfo-0:4.14.5-204.el8rhgs.x86_64 as a component of Red Hat Gluster 3.5 Samba on RHEL-8
  • libsmbclient-devel-0:4.14.5-204.el8rhgs.x86_64 as a component of Red Hat Gluster 3.5 Samba on RHEL-8
  • libwbclient-0:4.14.5-204.el8rhgs.x86_64 as a component of Red Hat Gluster 3.5 Samba on RHEL-8
  • libwbclient-debuginfo-0:4.14.5-204.el8rhgs.x86_64 as a component of Red Hat Gluster 3.5 Samba on RHEL-8
  • libwbclient-devel-0:4.14.5-204.el8rhgs.x86_64 as a component of Red Hat Gluster 3.5 Samba on RHEL-8
  • python3-samba-0:4.14.5-204.el8rhgs.x86_64 as a component of Red Hat Gluster 3.5 Samba on RHEL-8
  • python3-samba-debuginfo-0:4.14.5-204.el8rhgs.x86_64 as a component of Red Hat Gluster 3.5 Samba on RHEL-8
  • samba-0:4.14.5-204.el8rhgs.src as a component of Red Hat Gluster 3.5 Samba on RHEL-8
  • samba-0:4.14.5-204.el8rhgs.x86_64 as a component of Red Hat Gluster 3.5 Samba on RHEL-8
  • samba-client-0:4.14.5-204.el8rhgs.x86_64 as a component of Red Hat Gluster 3.5 Samba on RHEL-8
  • samba-client-debuginfo-0:4.14.5-204.el8rhgs.x86_64 as a component of Red Hat Gluster 3.5 Samba on RHEL-8
  • samba-client-libs-0:4.14.5-204.el8rhgs.x86_64 as a component of Red Hat Gluster 3.5 Samba on RHEL-8
  • samba-client-libs-debuginfo-0:4.14.5-204.el8rhgs.x86_64 as a component of Red Hat Gluster 3.5 Samba on RHEL-8
  • samba-common-0:4.14.5-204.el8rhgs.noarch as a component of Red Hat Gluster 3.5 Samba on RHEL-8
  • samba-common-libs-0:4.14.5-204.el8rhgs.x86_64 as a component of Red Hat Gluster 3.5 Samba on RHEL-8
  • samba-common-libs-debuginfo-0:4.14.5-204.el8rhgs.x86_64 as a component of Red Hat Gluster 3.5 Samba on RHEL-8
  • samba-common-tools-0:4.14.5-204.el8rhgs.x86_64 as a component of Red Hat Gluster 3.5 Samba on RHEL-8
  • samba-common-tools-debuginfo-0:4.14.5-204.el8rhgs.x86_64 as a component of Red Hat Gluster 3.5 Samba on RHEL-8
  • samba-debuginfo-0:4.14.5-204.el8rhgs.x86_64 as a component of Red Hat Gluster 3.5 Samba on RHEL-8
  • samba-debugsource-0:4.14.5-204.el8rhgs.x86_64 as a component of Red Hat Gluster 3.5 Samba on RHEL-8
  • samba-devel-0:4.14.5-204.el8rhgs.x86_64 as a component of Red Hat Gluster 3.5 Samba on RHEL-8
  • samba-krb5-printing-0:4.14.5-204.el8rhgs.x86_64 as a component of Red Hat Gluster 3.5 Samba on RHEL-8
  • samba-krb5-printing-debuginfo-0:4.14.5-204.el8rhgs.x86_64 as a component of Red Hat Gluster 3.5 Samba on RHEL-8
  • samba-libs-0:4.14.5-204.el8rhgs.x86_64 as a component of Red Hat Gluster 3.5 Samba on RHEL-8
  • samba-libs-debuginfo-0:4.14.5-204.el8rhgs.x86_64 as a component of Red Hat Gluster 3.5 Samba on RHEL-8
  • samba-pidl-0:4.14.5-204.el8rhgs.noarch as a component of Red Hat Gluster 3.5 Samba on RHEL-8
  • +14 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. For details on migrating Samba/CTDB configuration files, refer to: https://access.redhat.com/solutions/4311261 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) Workaround: Setting ~~~ dcesrv:max auth states=0 ~~~ in the smb.conf will provide some mitigation against this issue.

🔗 References (6)